telling

(archaic outside of idioms) To count, reckon, or enumerate.

"All told, there were over a dozen.  Can you tell time on a clock?  He had untold wealth."

To narrate.

"I want to tell a story;  I want to tell you a story."

To convey by speech; to say.

"Finally, someone told him the truth.  He seems to like to tell lies."

Having force, or having a marked effect; weighty, effective.

"a telling blow"

Revealing information; bearing significance.

"a telling smile"

Serving to convince.

"telling evidence"