what is the difference in these two words in terms of meaning or grammar?
which one to use here: say no or tell no? say one's name or tell one's name. we use tell a secret instead of say why is that? thanks a lot.
I wuold suggest that you tell someone something and that you say something to anyone/everyone.
Tell X your name - specifically to an individual
Say your name - generally, perhaps to make sure your name is understood.
He told me a secret - secrets are usually only told to people, otherwise they aren't secret.
(Note also that the more common collocation with 'name' is 'give' - which avoids the problem : 'He telephoned the poice, but refused to give his name.')