Zero-marking in English is the indication of a particular grammatical function by the absence of any morpheme (word, prefix, or suffix). The most common types of zero-marking in English involve zero articles, zero relative pronouns, and zero subordinating conjunctions. Examples of these are I like cats (where the absence of the definite article the signals that cats is an indefinite reference whose specific identity is not known to the listener), that's the cat I saw, in which the relative clause (that) I saw omits the implied relative pronoun that that would be the object of the clause's verb, and I wish you were here, in which the dependent clause (that) you were here omits the subordinating conjunction that.
In some varieties of English, grammatical information that other English varieties typically express with grammatical function words or bound morphemes may be omitted. For example, where most varieties of English utilize explicit plural morphemes (e.g. singular mango versus plural mangoes), West Indian creole speakers refer to plural objects without such morphology (I find one dozen mango.).
The lack of marking to show grammatical category or agreement is known as zero-marking or zero morpheme realization. This information is typically expressed with prepositions, articles, bound morphemes or function words in other varieties of English.