# Is "butane" an homologue of "butane"?

I take it your question relates to butane, $n - {C}_{4} {H}_{10}$, and but-2-ene, ${H}_{3} C - C H = C H C {H}_{3}$? No they are NOT homologues.
Butane is an alkane, with general formula ${C}_{4} {H}_{10}$. But-2-ene has general formula ${C}_{4} {H}_{8}$, and is an olefin, an alkene.
A useful concept to develop is the idea of the degree of unsaturation; each degree of unsaturation corresponds to a DOUBLE BOND or a RING. An carbon chain of $n$ carbons thus has $\left(2 n + 2\right)$ hydrogen atoms if it is saturated. You can see the relationship between butane, ${C}_{4} {H}_{10}$, and unsaturated ${C}_{4} {H}_{8}$ (it could be cyclobutane, but here it is butene). The ${C}_{4} {H}_{8}$ formula has 2 hydrogens less than the unsaturated formula, and thus an olefinic bond OR a ring junction MUST be present.