The dispute, in regard to construction delineation, largely originates from the blurring distinction of theoretical and operational conceptions. This study claims that constructions could be operationally delineated as the frequency-based form-meaning entrenchment which is verified through examining conditional probability among linguistic structures. Entrenchment is in line with constructions with regard to its gradualness, gradedness, and dynamicity. A conditional probability based collexeme analysis of relativizer omission by native speakers of English has revealed that a) relativizer omission should be classified as constructions on grounds of their entrenchment retrieved through conditional probability; b) distinct discrepancies could be verified between implicit/explicit relativizer constructions with the former geared towards concrete lexical dimension, thus requiring a lower cognitive load.