As few as possible, as mentioned above, but please, please can we all use 'STOP' or 'GO' in the event of a failure prior to V1?
Abandon, abort, reject, continue, keep going, just what are they all about?
"ABORT" seems the most unambiguous callout for aborting a takeoff.
"STOP"
Stop what?
"Abort" is unambiguous and stands out from common terms in ordinary speech like your "stop", and it is immediately clear in its interpretation without even an instant required to do so.
"You abort a takeoff" is simply more concise than "You stop a takeoff".