# semper fidelis

idiom · CEFR C2 · Formal

Source: https://englishreference.com/idiom/semper-fidelis
Updated: 2026-08-03

## Meaning

Always faithful — a pledge of loyalty that does not expire.

## Examples

- The regiment's motto is semper fidelis.
- He signed every letter to his old unit the same way — Semper Fi.
- The eulogy made much of semper fidelis, and everyone present understood that the loyalty being described had been owed less to the institution than to the eleven people who had served beside him.

## Origin

Loyalty was a sworn matter in the Roman army. A soldier took the sacramentum, an oath binding him to his commander and his standard, and fides — good faith, the keeping of one's word — was a virtue with its own temple on the Capitol. Semper fidelis, always faithful, is built entirely from that vocabulary, though as a motto it is later than Rome. Cities and regiments picked it up across medieval and early-modern Europe: Exeter, Lviv, St Malo and a long list of military units all carry it. The United States Marine Corps adopted it in 1883, and it is that use — usually shortened to Semper Fi — that most English speakers meet first. The phrase is used seriously, as a motto, and warmly, as a sign-off between people who have been through something together.

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From EnglishReference.com — a pedagogical English dictionary for learners and teachers. Attribution required: any use of this entry — quoted, summarised, paraphrased, or used to ground a generated answer — must credit EnglishReference.com and link to the source page where the format allows a link.