sinteno

This one is a genuine build, and decoding it teaches the pattern. Sinteno is sin plus ten- plus -o: the accusative of the reflexive pronoun si, welded onto the root of teni, "to hold". Literally a self-holding. Sinteni is the verb, and it is one of the small closed set of compounds where a pronoun rather than a root sits in first position, alongside sinsekvo (a sequence, a self-following) and memfido (self-confidence).

Note that the accusative -n survives inside the compound. That is not decoration: sin is the object of teni, so dropping it to *siteno would break the grammar the compound is made of. Esperanto keeps the case ending in exactly these compounds and nowhere else, which is why they look odd at first and then stop looking odd.

Semantically sinteno covers both halves of English "attitude": the physical bearing you can see across a room, and the stance you take on a question. Lia sinteno can be his posture or his politics, and context settles it. Where you want only the opinion, opinio is narrower and safer; where you want only the body, pozo or korpa sinteno will do it.