Contrastive descriptions can occur at every level of linguistic structure: speech sounds (phonology), written symbols (orthography), word-formation (morphology), word meaning (lexicology), collocation (phraseology), sentence structure (syntax) and complete discourse (textology). Various techniques used in corpus linguistics have been shown to be relevant in intralingual and interlingual contrastive studies, e.g. by 'parallel-text' analysis (Hartmann 1997).[6]