Meaning of "collat." in Lexicon

I’m wondering what “collat.” stands for and what that term actually means;

e.g.: “ὑπέσχημαι a collat. form of ὑπέχομαι”

Thanks in advance!

Collateral, according to the general list of abbreviations at the front: section V, p xivi

Thank you! I don’t have the physical LSJ, so that’s helpful.

Could someone explain what it means that a word is a collateral form of another word? Is it a kind of cognate?

It’s more than a cognate, it’s a by-form (cf. German bei-), a variant form of the same word.

It’s not strictly true that "ὑπέσχημαι [is] a collat. form of ὑπέχομαι”, because they are different tenses (ὑπέσχημαι perfect, ὑπέχομαι present). But it would be true to say that ὑπίσχομαι is a collateral form of ὑπέχομαι. Dialectal and semantic differences come into play.

That’s very helpful! Thank you for the explanation.