Objective: adjective
A word that’s very often mispronounced by non-natives is the noun adjective. Natives put the main stress at the beginning, Ádjective. But non-natives tend to skip the initial ad- and put the main stress in the middle, adjÉctive. Here are examples of the native pronunciation:
The non-native mistake isn’t surprising. For one thing, most three-syllable nouns beginning ad- have a weak first vowel and the main stress in the middle, e.g.
advÁntage, advÉnture, admÍrer, addÍction, admÍssion, adhÉsive, adjÚstment, advÁncement
Those with initial stress are less common, e.g.
Ádmiral, Ádvocate, Ádditive, Ádenoid
The pattern with words ending -ective is even clearer. Whether nouns or adjectives, these generally have the main stress in the middle, e.g.
objÉctive, perspÉctive, detÉctive, dirÉctive, subjÉctive, effÉctive, protÉctive, respÉctive, reflÉctive, selÉctive
As far as I’m aware, adjective is the only one with initial stress.
For comparison, here are examples of objÉctive used by natives:
Further notes
The second syllable of adjective can contain any one of three vowels, /ɪ/, /ə/ or /ɛ/.
The penultimate stress of words like adventure and admirer and the antepenultimate stress of words like advocate and admiral is related to the fact that the middle syllable is ‘heavy’ in the former but ‘light’ in the latter.
‘Adjective’ differs from those other ‘-ective’ words in having only ever been used as a noun, and arriving in English that way (there was ‘noun adjective’, but in English that’s better construed as apposition). Cf. perhaps ‘calumny’ for a parallel case with anomalous early stress.
k_over_hbarc at yahoo.com
… and (noun) ‘adjective’ was frequently paired with (noun) ‘substantive’, with the same stress (traditionally, and still in America).
Yes; the existence of BrE substántive presumably relates to its use as both noun and adjective. Some dictionaries do list adjective as an adjective, but this is obsolete or specialist. I don’t know if it ever had medial stress when used adjectivally.