Wikipedia gives literal translation as: Into the middle of things.

As far as I am aware intoin takes accusative.

Plural accusative of medium seems to be media, not medias

Even if I am mistaken in this way of thinking, there seems to be no medias word in declension table for medium.

Why does in medias res seem to be accepted form then?

  • What about “virtus est medium vitiorum” Horace Epistle I, 18 Si bene te novi ?
    – Chris Hoak
    Commented Jan 23, 2020 at 15:21

3 Answers 3


You are confusing two words:

  • The noun medium means "center".
  • The adjective medius means "central".

In this idiom one goes into "central things". The word res is feminine (the singular nominative and plural accusative happen to look alike), so the adjective has to be in feminine plural accusative: medias.

If you were to use the noun medium instead, you might want to go into "the center of things". Then you'd put medium in singular accusative (there's only one center, right?) and res in plural genitive. This leads to the alternative in medium rerum. This might be equally valid, but Latin does often prefer adjectives to nouns, and Horatius happened to write in medias res.

Using the adjective is probably more idiomatic and common than the noun, but the noun is not a non-Latin choice either. See this question and its answer for an example from Vergilius, where the noun medium is used although the adjective medius would have been metrically equal. Perhaps the adjective would not work here, as something happens between two things, not in the middle of one. But I would still take it as evidence (perhaps weak!) that both medius and medium are appropriate in cases like yours.


Medias is not a noun but an accusative of the adjective medius (middle or central) in agreement with the plural res. This is standard idiomatic usage, not just for this phrase. A spatial portion is consistently expressed (p. 168) in Latin with an adjective in a way that sounds wrong when taken word-for-word into English:

  1. 'The whole of,' 'the middle of,' 'the top (bottom) of,' 'the rest of,' are expressed in Latin by adjectives agreeing with nouns (instead of the partitive genitive)

The alternative in medium rerum constructed by Joonas Ilmavirta (using the accusative noun medium and the genitive rerum) is the closest word-for-word to the English "into the middle of things", but is not "equally valid" based on the Latin usage rule.

  • 1
    Welcome to the site! I agree that the adjective medius is a far more idiomatic choice here.
    – Joonas Ilmavirta
    Commented Aug 4, 2017 at 7:21
  • Good answer. The construction is indeed common in Latin, but less common in English or various other modern languages. We call this figure of speech enallage, "interchange, transposition", or hypallage: it applies when an adjective is made to agree syntactically with a certain substantive (pro)noun, while semantically it belongs with another one. Dutch Wikipedia explains it well enough (the English one is i.m.o. strange or less accurate): nl.wikipedia.org/wiki/Enallage English Wikipaedia explains it under hypallage: en.wikipedia.org/wiki/Hypallage
    – Cerberus
    Commented Jan 26, 2020 at 3:16

As the Latin preposition 'in' can govern either the accusative or the ablative case, depending on whether movement or place is expressed, it is grammatically correct to speak of (for example) an author plunging in medias res (into the midst of matters) to begin the presentation of a story, but (theoretically, at any rate) incorrect to say that a story begins in medias res as this is evidently place and not movement, and strictly should be in mediis rebus, the ablative form. But most people would dismiss this as pedantry, like trying to put status quo into the ablative.

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