nonconjugation

Nonconjugation, in linguistics, refers to the limited or absent inflection of verbs for tense, aspect, mood, person, or number. In such languages, verbs typically do not change form to express grammatical relations; instead, reliance is placed on word order, helper words, particles, or adverbs to convey meaning. Many isolating or analytic languages exhibit nonconjugation to varying degrees; examples include Mandarin Chinese, Indonesian, and Vietnamese. However, even languages described as nonconjugating may have some analytical devices; there can be periphrastic constructions for past, future, or aspect.

In organic chemistry, nonconjugation means the lack of π-electron delocalization across adjacent p orbitals. It occurs when the π orbitals are not in a continuous overlapping sequence, such as when an sp3 center interrupts a chain of double bonds, or in cross-conjugated systems where delocalization is confined to separate branches. Nonconjugated systems tend to have larger energy gaps between the highest occupied and lowest unoccupied molecular orbitals (HOMO and LUMO), different UV–visible absorption, and different reactivity compared with conjugated systems. Examples include hydrocarbons with saturated segments separating double bonds, or aliphatic segments in polymers.