In linguistics, word order (also known as linear order) is the order of the syntactic constituents of a language. Word order typology studies it from a cross-linguistic perspective, and examines how different languages employ different orders. Correlations between orders found in different syntactic sub-domains are also of interest. The primary word orders that are of interest are

• the constituent order of a clause, namely the relative order of subject, object, and verb;
• the order of modifiers (adjectives, numerals, demonstratives, possessives, and adjuncts) in a noun phrase;
• the order of adverbials.

Some languages use relatively fixed word order, often relying on the order of constituents to convey grammatical information. Other languages—often those that convey grammatical information through inflection—allow more flexible word order, which can be used to encode pragmatic information, such as topicalisation or focus. However, even languages with flexible word order have a preferred or basic word order, with other word orders considered "marked".

Constituent word order is defined in terms of a finite verb (V) in combination with two arguments, namely the subject (S), and object (O). Subject and object are here understood to be nouns, since pronouns often tend to display different word order properties. Thus, a transitive sentence has six logically possible basic word orders:

• about half of the world's languages deploy subject–object–verb order (SOV);
• about one-third of the world's languages deploy subject–verb–object order (SVO);
• a smaller fraction of languages deploy verb–subject–object (VSO) order;
• the remaining three arrangements are rarer: verb–object–subject (VOS) is slightly more common than object–verb–subject (OVS), and object–subject–verb (OSV) is the rarest by a significant margin.