deltoid

1 of 2

noun

del·​toid ˈdel-ˌtȯid 

: a large triangular muscle that covers the shoulder joint and serves to raise the arm laterally

deltoid

2 of 2

adjective

1

: having a triangular shape

a deltoid leaf

see leaf illustration

2

: relating to, associated with, or supplying the deltoid

Did you know?

The fourth letter of the Greek alphabet is delta, and a capital delta is triangle-shaped. In English, delta commonly means the sand deposits that form a huge triangle at the mouth of certain large rivers. Deltoid as an adjective means "having a triangular shape", and botanists often use the word to describe the shape of certain leaves. The triangular, swept-back wings seen on jet fighter aircraft are called delta wings. Your deltoid muscles—not far from your rhomboids—form a cap on your shoulders, and some gym trainers even treat shoulder and deltoid as synonyms. Can you guess the general shape of deltoids when seen from the side?

Examples of deltoid in a Sentence

Recent Examples on the Web

Noun

This move primarily works your lats, rhomboids, and traps, plus your core, biceps, and deltoids. —Amy Marturana Winderl, SELF, 9 Oct. 2024

When the body is sedentary, muscles—including the glutes, but also the deltoids, pectorals, hamstrings, and more—aren't engaged or working, Bach said. —Alyssa Hui, Health, 2 Aug. 2024

Adjective

Chest press targets the pectoral, deltoid, and tricep muscles. —Alyssa Hui, Verywell Health, 28 Apr. 2023

The deltoid muscle has three parts: the anterior, the medial/lateral, and the posterior. —David Otey, Men's Health, 10 Feb. 2023

Word History

Etymology

Noun

New Latin deltoides, from Greek deltoeidēs shaped like a delta, from delta

First Known Use

Noun

circa 1681, in the meaning defined above

Adjective

circa 1753, in the meaning defined at sense 1

Medical Definition

deltoid

1 of 2 noun

del·​toid ˈdel-ˌtȯid 

: a large triangular muscle that covers the shoulder joint, serves to raise the arm laterally, arises from the upper anterior part of the outer third of the clavicle and from the acromion and spine of the scapula, and is inserted into the outer side of the middle of the shaft of the humerus

called also deltoid muscle

see deltoid tuberosity

deltoid

2 of 2 adjective

: relating to, associated with, or supplying the deltoid

the deltoid branch of the thoracoacromial artery