I'm looking for a French synonym for "secondaire" which doesn't have that connotation that the thing is accessory (not necessary). The sense I would want is something that is built on something else that is "primaire". I've been thinking about "complexe, composé", but it doesn't feel quite right.. I can't even find a word in English.
An example would be useful. I will try fo figure out one.
Son fusil enrayé, il sortit son arme secondaire.
Son fusil enrayé, il sortit sa deuxième arme.
I don't feel this deuxième weapon is accessory.
Perhaps complémentaire, but the sentence won't be natural. It will more likely be:
Son arme principale enrayée, il sortit son arme secondaire.
This arme secondaire is not accessory, here it's the correct word in French.
Others candidates: alternatif (somewhat critized in formal French because une alternative is not another option, but both options as a whole), adjoint, associé, d'appui, d'appoint..