What's the difference between using Is.... and Ta...?
is is use for classification/identification sentences (at this level), whereas bí (tá is a form of bí) can't be used for those. It's very similar to ser versus estar in Spanish
The reason I asked is because Ta seems to be used for classification/identification (_ is __-type sentences) a lot, when I thought Is would be used. I don't know Spanish, so I don't know the difference between ser and estar.
bí can be, in certain sentences, like tá sé ina dhoctúir. But that has a different meaning. Do you have any other examples?
I know "I am a doctor" is "is doctuir me" (still can't do accents in comments), but why is the sentence above (Water is important) not "is uisce riachtanach?"
Riachtanach is an adjective. You're describing what water is, not classifying or identifying it as something, which generally requires another noun.
In Spanish one uses ser, not estar, for "necesario". Hence I used "is" instead of "bí". It is clearly a bit different in Irish.
Yes. The comparison with Spanish isn't one-to-one. generally, if you're linking two nouns (including pronouns), you use is. Otherwise, bí.
Re: "tá" vs. "is" -
What about the seanfhocal: "Is glas iad na cnoic i bhfad uainn." Isn't "faraway hills" being linked to the adjective, "green"?