A written short form of the word 'society'. You will see it in the names of organisations, especially old and formal ones, where it saves space: 'Royal Soc. of Chemistry', 'Amer. Chem. Soc.' It nearly always appears with a capital S and a full stop after it, because it is a shortened name, not a word in its own right.

This is writing only. When you read the name aloud, you say the whole word 'society'. Nobody says 'sock' or spells out the letters. You will meet it mainly in academic references, journal titles, library catalogues, letterheads, and lists of organisations — places where space is tight and the reader already knows what is meant.

Be careful in reading: 'soc.' in a footnote can also stand for other things depending on the field, and a lowercase 'soc' with no stop is a casual short form of 'social' or 'sociology' in student talk ('soc sci', 'my soc class'). Those are different from this one. Here it is 'society', capital S, with the stop.