tea vs sun tea

tea and sun tea both are nouns.

Word	Noun	Adjective	Verb	Adverb
tea	Yes	No	No	No
sun tea	Yes	No	No	No

As nouns, sun tea is a hyponym of tea; that is, sun tea is a word with a more specific, narrower meaning than tea:

tea: a beverage made by steeping tea leaves in water
sun tea: tea made by exposing tea leaves steeped in water to the direct rays of the sun; usually served with ice

Other hyponyms of tea include cambric tea, cuppa, cupper, herb tea, herbal, herbal tea, ice tea, iced tea, white tea.

tea (noun)	sun tea (noun)
a beverage made by steeping tea leaves in water	tea made by exposing tea leaves steeped in water to the direct rays of the sun; usually served with ice
a light midafternoon meal of tea and sandwiches or cakes
dried leaves of the tea shrub; used to make tea
a tropical evergreen shrub or small tree extensively cultivated in e.g. China and Japan and India; source of tea leaves