Some tea has caffeine, most has don't.

all tea has caffeine unless it's decaf. some things that aren't tea are called tea casually, but they aren't tea, for instance peppermint "tea" is not tea. by the same logic that one would call peppermint a tea, one would have to call coffee a tea. and beef broth.

no true scotsman tea. Tea is what is called tea. You can not just decide that you don't like some teas so they are not tea anymore.

That depends on culture. All camelia s. teas have it (green etc) but almost none of common herbal teas in Europe have it (chamomile, menta, sage etc.) They are not called casually teas.

> They are not called casually teas.

are you saying chamomile isn't called tea but it's one of the teas without caffeine? if so that's very confused.

camelia sinensis is tea. when i said that other things are casually called tea, i mean that what chamomile tea, for example, ought to be called is a tisane or an herbal infusion. casually, people might call it a tea; some people are so casual about it that they think it actually is tea. but it isn't.