# Terminology: words with only terminals vs. words which can contain nonterminals

In the context of formal grammars, is there a standard terminology to distinguish

• words (i.e., finite sequences of letters/tokens) which only contain terminal letters/tokens, and

• words which may contain nonterminals?

I prefer to use the term "word", unqualified, to refer to the former, because I am discussing various ways to produce words over a fixed alphabet $\Sigma$ (of terminals!), the set of nonterminals can vary from grammar to grammar, so words over them only make sense for a particular grammar. But I would still like to have a term to refer to words which may contain nonterminals: how should I best call them?

"Nonterminal words" isn't a good term because they might turn out to have only terminals; "possibly nonterminal words" or "not necessarily terminal words" is too long and syntactically awkward. "Word over $\Sigma\cup N$" is, of course, perfectly clear, but sometimes one doesn't want to introduce any symbols. What other options are available? From this related question I'm thinking maybe "symbol string" or "symbol word", but I'm not sure whether it's sufficiently distinctive. Some other possibilities are "generalized word" or perhaps "form" since the generalized words which can be derived from a grammar are called "sentential forms". Any other idea?

• @fade2black You can always partition an alphabet. Grammars do nothing else: sentential forms are words/sentences over $\Sigma' = \Sigma \cup N$. Not really special, unless you add the "can be derived" clause to the definition of the term. (Which I don't think we do, because then we couldn't ask, "Does G generate this sentential form?") – Raphael Oct 10 '17 at 19:26