Using Linguistic Criteria to Define Multiword Units

To describe the infinite set of sentences expressed in a Natural language, one needs to define the finite set of its atomic units, i.e., its vocabulary, and the rules that combine these atomic units to construct sentences, i.e., its grammar. However, separating the vocabulary from the grammar is not straightforward; one crucial problem is defining multiword units. Here, I present three reproducible criteria to characterize them and thus separate the vocabulary from the grammar in an operational way.