Is ss a word in Scrabble?

In official Scrabble, ss is not a valid word on its own in standard play using the NASPA Word List or Collins Scrabble Words. The two-letter combination SS is not recognized as a standalone English word in those official dictionaries, unlike other two-letter combinations like aa, ab, ad, ae, ag, ah, ai, al, am, an, ar, as, at, aw, ax, and ay, which are valid. SS is sometimes used as an abbreviation for Schutzstaffel in historical contexts, as an abbreviation for steamship, or as a plural marker, but abbreviations are generally not allowed in Scrabble unless they are listed as words. However, SS can appear as part of valid plays. For example, you can form words that contain double S, such as boss, less, mass, and you can play an S next to an existing S to form two separate words that both remain valid, such as forming as and is in the same play. In some casual house rules, players might allow ss as a word meaning to hiss, but in tournament Scrabble, it is not allowed. If you need to use two S tiles, it is better to play them as separate one-letter extensions forming valid two-letter words or as part of longer words that include double S.