Where available, I have linked to a relevant Wikipedia article:
Agastya. a rishi, numbered among the great Saptarishi (Seven Sages).
Agni. god of fire.
Ahalya. wife of the rishi Gautama.
Aja. king of Ayodhya; father of Dashratha, Rama's father.
Akampana. son of Sumali; brother of Kaikashi; maternal uncle of Ravana.
Aksha. youngest son of Ravana and Mandodari.
Anaranya. an ancient king of Ayodhya; Rama's remote ancestor.
Anasuya. wife of the rishi Atri.
Anga. an ancient kingdom of eastern India; home of Rishyasringa.
Angada. son of Vali and Tara; Rama's ally, later the King of Kishkindha.
Anjana. mother of Hanuman; according to some, daughter of Ahalya and Gautama.
apsaras. celestial beings of great beauty associated with music and dancing; the gods often send apsaras to distract rishis from their meditation.
Aruna. divine charioteer of Surya, the sun-god.
Aruna. female form of the charioteer of Surya, the sun-god.
Arundhati. wife of the rishi Vashishtha; associated with the morning star.
ashoka. a flowering tree; Ravana kept Sita in the Ashoka Vatika, Ashoka Grove.
ashram. the secluded home of a holy person, sometimes called a hermitage in English (home of a hermit).
Ashwapati. king of Kekeya; father of Kaikeyi, wife of Dasharatha.
astras. supernatural weapons imbued with the powers of gods or natural forces.
asuras. supernatural beings of great power, often engaged in hostilities with the devas or humans; sometimes translated as "demons" in English.
Atri. a rishi, numbered among the great Saptarishi (Seven Sages); husband of Anasuya.
Ayodhya. capital of the kingdom of Kosala, ruled by King Dasharatha and, later, by King Rama.
Ayomukhi. a cave-dwelling rakshasi.
Benjakai. a rakshasi with magical powers; daughter of Vibhishana (she appears in the Thai Ramakien).
Bharata. Rama's brother; son of Dasharatha and Kaikeyi.
Bhasmalochana. a rakshasa warrior.
Bhudevi. goddess of the earth; also called Bhumi.
Bhumi. goddess of the earth; also called Bhudevi.
Brahma. god of creation; consort of the goddess Saraswati.
Brahma-arrow. weapon given to Rama by rishi Agastya.
Brahman. the Ultimate Reality, the cause of everything.
Brahmastra. the Brahma-weapon, an astra able to destroy the world.
brahmin. members of the priestly class.
Chandra. god of the moon.
Chandrahasa. a sword that Shiva gave to Ravana.
Dadhimukha. guardian of the honey-grove in Kishkindha.
danavas. a type of asura, often at war with the devas; sometimes translated as "demons" or "giants" in English.
Dashagriva. name given to Ravana at birth, meaning "Ten-Necked".
Dasharatha. king of Ayodhya; father of Rama, Bharata, Shatrughna and Lakshmana.
deva. a divine being or god.
devi. a divine being or goddess.
dharma. that which is right and true; duty; justice.
Dilipa. king of Ayodhya; Rama's great-great-grandfather.
Dundhubi. asura in the form of a bull; son of Mayasura and Hema; father of the asura Mayavi.
Durga. goddess of war; manifestation of the goddess Parvati.
Durvasa. a rishi, notorious for his bad temper; son of Anasuya and Atri.
Dushana. a rakshasa warrior.
gandharvas. celestial musicians.
gandharvi. a female gandharva.
Garuda. divine bird; the vehicle of the god Vishnu.
Gautama. a rishi, numbered among the great Saptarishi (Seven Sages); husband of Ahalya.
gopis. female cowherd; the gopis of the village of Vrindavan loved Krishna, and he loved them.
Guha. chief of the Ganga ferrymen who takes Rama across the river.
guru. teacher, guide, expert.
Haihaya. an ancient kingdom of central India; ruled by King Kartavirya.
Hanuman. divine monkey who is a faithful follower of Rama; his mother is Anjana, and his divine father is Vayu, the wind-god.
Hema. apsara; wife of Mayasura; mother of Mandodari and Dundhubi.
hijra. people of the third gender (not male, not female); transgender people.
Himalayas. mountain range in northern India.
Ilavida. a wife of rishi Vishrava, mother of Kubera.
Ilvala. a rakshasa; brother of Vatapi.
Indra. god of storms and the sky; guardian of the eastern direction.
Indrajit. son of Ravana and Mandodari; born with the name Meghanada, he earned the name Indrajit (Indra-Conqueror) to defeating the god Indra.
Jambavan. king of the bears; ally of Rama.
Janaka. king of the Videha kingdom; adopted father of Sita.
jatas. Sanskrit word for matted, twisted hair (dreadlocks).
Jatayu. mighty bird (eagle or vulture); brother of Sampati; friend of Dasharatha.
Kabandha. a rakshasa without a head; originally a gandharva named Vishvavasu cursed to become a rakshasa.
Kaikashi. daughter of the rakshasa king, Sumali; wife of the rishi Vishrava; mother of Ravana.
Kaikeyi. wife of King Dasharatha; mother of Bharata.
Kailasha. a peak in the Himalayas; home of the god Shiva.
Kala. god of time, associated with destiny and with death.
Kali. goddess of war; manifestation of the goddess Parvati.
Kartavirya. thousand-armed king of Haihaya.
Kasur. a city in the Punjab to the south of Lahore; now in Pakistan.
Kaushalya. chief wife of King Dasharatha; mother of Rama.
Kekaya. an ancient kingdom of nothern India; ruled by King Ashwapati, father of Kaikeyi.
Khara. a rakshasa warrior.
Khatvanga. king of Ayodhya; Rama's great-great-great-grandfather.
kheer. a sweet rice pudding, also called payasam.
Kishkindha. the kingdom of the monkeys ruled by King Vali, later by King Sugriva.
Kosala. an ancient kingdom of northern India with its capital in Ayodhya.
Krishna. the eighth avatar of the god Vishnu (following Rama, the seventh avatar); he is a major character in the epic Mahabharata.
Kubera. king of the yakshas; son of Vishrava and Ilavila; half-brother of Ravana; guardian of the northern direction.
Kubja. a woman with a hunched back cured by Krishna; some consider her a future incarnation of Manthara, while others see her as an incarnation of Shurpanakha.
Kumbhakarna. Ravana's brother; son of Vishrava and Kaikashi; he is gigantic in size and cursed to be asleep almost all the time.
Kusha. son of Rama and Sita.
kusha grass. a sacred plant of India; Desmostachya bipinnata, called "salt reed-grass" in English.
Lahore. a city in the Punjab; modern Lahore is in Pakistan.
Lakshmana. Rama's brother; son of King Dasharatha and Sumitra.
Lakshmi. goddess of wealth; the consort of the god Vishnu.
Lanka. home of Ravana, King of the Rakshasas; the "Golden City".
Lankini. divine protectress of Lanka, home of the rakshasas.
Lava. son of Rama and Sita.
Lavapuri. Lava-City; a city founded by Rama's son, Lava; associated with the modern city of Lahore.
Macchanu. son of Hanuman and Suvannamaccha.
Madhuvana. a honey-park (Madhu-Vana) belonging to King Sugriva of Kishkindha.
Mahendra. legendary mountain range on the eastern coast of India.
Mainaka. legendary flying mountain that hides in the ocean.
Mandakarni. a rishi who lives with five apsaras in Panchapsaras (Five-Apsara) Lake.
Mandavi. daughter of Kushadhwaja, Janaka's brother, and thus cousin to Sita; wife of Bharata, Rama's brother.
Mandodari. wife of Ravana; mother of Indrajit and Aksha; daughter of Mayasura and Hema.
Manthara. loyal servant of Queen Kaikeyi; she has a humped back .
mantra. sacred words or sounds; some supernatural weapons are controlled by mantras.
Maricha. a rakshasa; son of Tataka; brother of Subahu.
Marutta. a king mentioned in the Uttara Kanda of Valmiki's Ramayana.
Matali. the charioteer of the god Indra.
Matanga. a rishi whose ashram was on Rishyamukha Hill in the kingdom of Kishkindha.
Matrikas. group of mother-goddesses (some say there are seven, some eight).
maya. an illusory show that people mistake for reality.
Mayasura. architect among the asuras; husband of Hema; father of Mandodari and Dundhubi.
Mayavi. asura; son of the asura Dundhubi.
Meghanada. the birth name of the son of Ravana and Mandodari later known as Indrajit.
Mithila. capital city of the ancient kingdom of Videha.
nagas. divine snake-beings with supernatural powers.
Nala. a monkey-son of Vishvakarma who builds a bridge for Rama.
Nalakubara. son of Kubera, king of the yakshas; husband of Rambha.
Nandana-Vana. the "Pleasure-Garden" in Indra's heaven.
Nandi. divine bull; the vehicle of the god Shiva.
Narada. a divine rishi who like to tell stories, share wisdom, and sometimes stir up trouble.
Nidra. goddess of sleep; Urmila Nidra refers to the long sleep of Urmila, wife of Lakshmana.
Padma. "Lotus," the daughter of King Padmaksha.
Padmaksha. "Lotus-Eyed," a king, father of Princess Padma.
Pampa. a lake in southern India; one of the five sacred lakes of India.
Panchapsaras. "Five-Apsaras," a lake inhabited by five apsaras and the rishi Mandakarni.
Panchavati. a location on the Godavari River in western India, now called Nashik.
Parashurama. the son of rishi Jamadagni; "Axe-Rama" who used the axe as one of his weapons; considered to be the sixth avatar of Vishnu.
Parvati. goddess of fertility and power; consort of the god Shiva.
Prahasta. a rakshasa, one of Ravana's generals.
Pratyangira. goddess of war; manifestation of the goddess Parvati.
puja. a devotional ritual which may include offerings of food or flowers to the divinity.
Pulastya. a rishi, numbered among the great Saptarishi (Seven Sages); father of Vishrava.
Pushpaka. a flying chariot belonging to Kubera, later stolen by Ravana.
Raghu. king of Ayodhya; great-grandfather of Rama.
rakshasa. shape-shifting supernatural beings, hostile to both gods and humans; sometimes translated as "demons" in English.
rakshasi. a female rakshasa.
Rama. son of Dasharatha, king of Ayodhya; later king of Ayodhya; considered to be an avatar of the god Vishnu.
Rama-fruit. a fruit called "custard-apple" in English.
Ramachandra. another name of Rama: Rama-Moon (chandra means moon).
Ramayana. the title of Valmiki's poetic composition about Rama's adventures: Rama-Ayana, Rama's Journey.
Rambha. apsara; wife of Nalakubara, son of Kubera.
Ratnakar. a bandit who, according to legend, later became the rishi Valmiki.
Ravana. king of the rakshasas in Lanka; son of Vishrava and Kaikashi; husband of Mandodari.
Rishabha Hill. a peak in the Himalayas where Hanuman sought healing herds.
Rishyamukha Hill. site of Matanga's ashram where Sugriva sought refuge from his brother Vali.
Rishyasringa. son of the rishi Vibhandaka; raised in complete isolation from all women.
Ruma. Ruma, the wife of Sugriva; Sugriva's brother Vali claimed her when he chased Sugriva away.
Sampati. mighty bird (eagle or vulture); brother of Jatayu.
sanjivani. a healing herb found in the Himalayas.
Sanskrit. ancient language of India; Valmiki composed his Ramayana in Sanskrit.
Saptarishis. the Seven Rishis, or Seven Sages, of India.
Saraswati. goddess of wisdom; consort of the god Brahma.
Sarayu. a river in northern India that flows past the city of Ayodhya.
Shabari. an old woman who lived in an abandoned ashram, awaiting Rama's arrival.
Shambara. a rakshasa who challenged the god Indra.
Shambuka. a low-born person of Ayodhya who performed the religious practices reserved for high-born brahmins.
Shanta. daughter of Dasharatha and Kaushalya.
Sharabhanga. a rishi whom Rama visits in the forest.
Sharanga. the bow of the god Vishnu.
Shatrughna. Rama's brother; son of King Dasharatha and Sumitra.
Shiva. the destuction-god; consort of the goddess Parvati.
Shrutakirti. daughter of Kushadhwaja, Janaka's brother, and thus cousin to Sita; wife of Shatrughna, Rama's brother.
shudra. of the four classes (brahmins, kshatriyas, vaishyas, shudras), the shudra class is the lowest.
Shurpanakha. a rakshasi; sister of Ravana.
Simhika. a monstrous asura able to control shadows.
Sita. adopted daughter of Janaka; wife of Rama; consider to be an avatar of the goddess Lakshmi.
Sita-fruit. a fruit called "sweet-apple" in English.
Subahu. son of the rakshasi Tataka; brother of Maricha.
Sugriva. younger brother of Vali; after Vali's death, King of Kishkindha; husband of Ruma.
Sulochana. wife of Indrajit; also known by the name Promila or Pramila.
Sumali. a rakshasa; father of Kaikashi, mother of Ravana.
Sumantra. royal charioteer of King Dasharatha.
Sumitra. wife of King Dasharatha; mother of Lakshmana and Shatrughna.
Sunaina. wife of King Janaka; adopted mother of Sita.
Suparshva. honorable rakshasa serving Ravana's court.
Surasa. supernatural being who attacks Hanuman on his way to Lanka.
Surya. god of the sun.
Sutikshna. a rishi whom Rama visits in the forest.
Suvannamaccha. mermaid; lover of Hanuman; mother of Hanuman's son Macchanu.
Swayamprabha. holy woman; friend of the apsara Hema.
Tamasa. a supernatural weapon, "darkness," in Ravana's possession.
Tara. wife of Vali, king of Kishkindha; mother of Angada.
Taranisen. a rakshasa; son of Vibhishana (his story appears in the Bengali Ramayana).
Tataka. born a yakshi, she was cursed to become a rakshasi; mother of Maricha and Subahu.
Tenalirama. jester and poet in the court of King Krishnadevaraya in the sixteenth century.
Trijata. one of the rakshasi guardians of Sita in the Ashoka Grove; considered by some to be a daughter of Vibhishana.
Tumburu. gandharva; cursed to live as the rakshasa Viradha.
Urmila. daughter of Janaka and Sunaina; sister of Sita; wife of Lakshmana.
Vaishravana. another name of Kubera.
Vali. son of the god Indra; king of Kishkindha; husband of Tara; father of Angada.
Valmiki. a rishi; the world's first poet, he composed the Ramayana in verse.
Varuna. god of the sea; guardian of the western direction.
Vashishtha. a rishi, numbered among the great Saptarishi (Seven Sages); household priest of King Dasharatha of Ayodhya.
Vasuki. king of the nagas.
Vatapi. a rakshasa; brother of Ilvala.
Vayu. god of wind.
Vedavati. a woman dedicated to Vishnu; considered by some an avatar of the goddess Lakshmi, an earlier incarnation of Sita.
veena. a stringed musical instrument like a lute.
vermillion. a bright red powder, called sindoor in India, worn by married women in the part of their hair.
Vibhandaka. father of Rishyasringa, whom he raised in complete isolation.
Vibhishana. brother of Ravana, a rakshasa famous for his righteous behavior.
Videha . an ancient kingdom of nothern India; ruled by King Janaka.
Vidyutjiva. rakshasa; husband of Shurpanakha.
Virabahu. son of Ravana (his story is found in the Bengali Ramayana).
Viradha. rakshasa; originally a gandharva named Tumburu cursed to become a rakshasa.
Vishnu. god of preservation; consort of the goddess Lakshmi.
Vishrava. a rishi; father of Ravana and of Kubera.
Vishvakarma. god of architecture.
Vishvamitra. a rishi, numbered among the great Saptarishi (Seven Sages); the guru of Rama and Lakshmana.
Vishvavasu. gandharva; cursed to live as the rakshasa Kabandha.
yagna. a ritual offering to a god or goddess.
yaksha. spirits of mountains, woods, lakes, and so on; sometimes translated as "fairies" in English.
Yama. god of death and of justice; guardian of the southern direction.
yojana. a measure of distance; appx. 8 miles or 12 kilometers.