'nonarchitectural' is formed in modern English by adding the prefix 'non-' (meaning 'not') to 'architectural.' 'Architectural' derives from 'architect' + the adjectival suffix '-al.'

'architect' originates from Greek 'architektōn' (ἀρχιτέκτων), from 'archi-' meaning 'chief' and 'tekton' meaning 'builder.' It passed into Latin and Old French, entered Middle English as 'architect,' and later produced the adjective 'architectural.' The prefix 'non-' comes from Latin 'non' meaning 'not' and has been used in English to form negations since the modern period; 'nonarchitectural' is a modern compound formed by prefixation.

Originally, 'architectural' referred specifically to matters of building design and structure; with the prefix 'non-' the compound simply denotes negation—'not relating to architecture'—a straightforward semantic formation rather than a major meaning shift.