In linguistics and literature, periphrasis (/pəˈrɪfrəsɪs/) is the use of a larger number of words, with an implicit comparison to the possibility of using fewer. The comparison may be within a language or between languages. For example, "more happy" is periphrastic in comparison to "happier", and English "I will eat" is periphrastic in comparison to Spanish comeré.

The term originates from the Greek word περιφράζομαι periphrazomai 'talking around', and was originally used for examples that came up in ancient Greek. In epic poetry, it was common to use periphrasis in examples such as "the sons of the Achaeans" (meaning the Achaeans), or "How did such words escape the fence of your teeth?" (adding a layer of poetic imagery to "your teeth"). Sometimes periphrastic forms were used for verbs that would otherwise be unpronounceable. For example, the verb δείκνυμι deiknumi 'to show', has a hypothetical form *δεδείκνται dedeikntai, which has the disallowed consonant cluster -knt-, so one would instead say δεδειγμένοι εἰσί dedeigmenoi eisi, using a periphrasis with a participle.

In modern linguistics, the term periphrasis is typically used for examples like "more happy": the use of one or more function words to express meaning that otherwise may be expressed by attaching an affix or clitic to a word. The resulting phrase includes two or more collocated words instead of one inflected word. Periphrastic forms are a characteristic of analytic languages, whereas the absence of periphrasis is a characteristic of synthetic languages. While periphrasis concerns all categories of syntax, it is most visible with verb catena.^{[clarification needed]} The verb catenae of English (verb phrases constructed with auxiliary verbs) are highly periphrastic.

The distinction between inflected and periphrastic forms is usually illustrated across distinct languages. However, comparative and superlative forms of adjectives (and adverbs) in English provide a straightforward illustration of the phenomenon. For many speakers, both the simple and periphrastic forms in the following table are possible:

The periphrastic forms are periphrastic by virtue of the appearance of more or most, and they therefore contain two words instead of just one. The words more and most contribute functional meaning only, just like the inflectional affixes -er and -est.

Such distinctions occur in many languages. The following table provides some examples across Latin and English:

Periphrasis is a characteristic of analytic languages, which tend to avoid inflection. Even strongly inflected synthetic languages sometimes make use of periphrasis to fill out an inflectional paradigm that is missing certain forms. A comparison of some Latin forms of the verb dūcere 'lead' with their English translations illustrates further that English uses periphrasis in many instances where Latin uses inflection.

English often needs two or three verbs to express the same meaning that Latin expresses with a single verb. Latin is a relatively synthetic language; it expresses grammatical meaning using inflection, whereas the verb system of English, a Germanic language, is relatively analytic; it uses auxiliary verbs to express functional meaning.