Relation between "concept" and "conception"

Generally, concept is used when referring to an objective idea/entity (as in the concept of eleven dimensions is hard to grasp), while conception refers to a certain person's subjective idea of something (as in his conceptions about English seem a little misguided). The difference, then, on at least one level, is objectivity.

Inflection refers to the modification of a word to express different grammatical categories (e.g. hitting is an inflected form of hit). This does not apply here. The only difference between the two nouns concept and conception is in meaning and usage.

Concept is derived from Latin conceptum, the past participle of concipio, and meant ‘that which is conceived’ (but not sexually). Conception is also ultimately from the same Latin verb, but comes to us via the noun conceptio, of which one meaning was 'the act of becoming pregnant'. That is the meaning it had when it first appeared in English in the early fourteenth century, but it soon started to be used figuratively for ‘the action or faculty of conceiving in the mind, or of forming an idea or notion of anything; apprehension, imagination.’

The relation between the two words is thus to be sought in Latin rather than English. It appears not to be the case, for instance, that conception is formed from concept by the addition of the suffix –ion.