いけない

Meanings

Expression, い-adjective bad; wrong; naughty
must not (do, be); should not; ought not to (after the -te form of a verb or adjective)
useless; no good; bad
hopeless; beyond hope
unfortunate; a shame; a pity (used to express sympathy)
unable to drink (alcohol)
so as not to ...; so that ... (won't); in case ...; for fear that ...; lest ... (as ...（すると／しては）～（から／ので）)

And 3 more.