not just -s but -as, -is. Endings of words in a language give a distinct flare to the language. What would latin sound like with out the -us/-um at the ends of its words? I dont have much experience though with baltic languages spoken in front of me, I do with greek though as I worked at a greek owned buisness once. When my one lithuanian friend in england did speak it, one of my first thoughts was that there is something similar about it to greek. Obviously they dont sound identical.