I am looking for ways to describe collaboration in Latin. My main interest is scientific collaboration, if the type matters. I would like to have both a verb "to collaborate" and a noun "collaboration". These English words have obviously a Latin origin, but I have been unable to find collaborare or collaboratio in Latin dictionaries, so I assume they are not found in classical literature. Are there better words for this kind of thing? I prefer attested classical expressions, but later ones are also welcome.
For referring to a collaborator, have you thought of socius or adiutor? The latter does not necessarily imply a subordinate role and can quite well be used of equals in a partnership. Each has a wide range of application, but the sense is always of working together in the same enterprise.
To describe a collaboration on matters scientific, it's probably better to try working round the subject. This would allow you to use such words/phrases as una experire to imply the relationship between co-workers: e.g. Gaius et Marcus una operabantur.
None of this is in the way of objecting to collaborare, etc., which strike me as perfectly valid but not quite the thing for a scientific dissertation in proper classical style - if that's what you want.
I have found collaboro/collaborare in the Gaffiot (lit. work in concert) with reference to cum, laboro and Tertullian On Repentance :
Non potest corpus de unius membri vexatione laetum agere: condoleat universum et ad remedium conlaboret necesse est.
De Paenitentia, Tertulliani
A translation uses "join with one consent". The same dictionary provided collega (colleague) and collegarius (one of the colleagues), refering to cum, lego and noting conlega sapientae from Cicero's De natura deorum :
Metrodori vero, qui est Epicuri collega sapientiae, multa inpudentiora recitabat; accusat enim Timocratem, fratrem suum, Metrodorus, quod dubitet omnia, quae ad beatam vitam pertineant, ventre metiri, neque id semel dicit, sed saepius.
De natura deorum, Cicero
A translation says co-partner in philosophy, which feels like some colleague...
collaboro or conlaboro is also in L/S, with the same unique reference to the early Christian author Tertullian (who writes fairly decent classicising Latin). It is a correctly formed prefixed verb and I would think it mere chance that it is not attested in classical authors.
My suggestion may or may not fit the spirit of your question, but the Creator ineffabilis (Student's Prayer of Thomas Aquinas) is beautifully written and includes a request that God collaborate with the three stages of a student's work:
These are all classically attested words (obviously), though they certainly are not stand-ins for the more prosaic "collaborate."