✨📕 The NEWThe NEW Collegiate Dictionary, 12th Edition Over 5,000 words added — Buy Now! Collegiate Dictionary — Buy Now!

per os

adverb

ˌpər-ˈōs How to pronounce per os (audio)
: by way of the mouth
medication administered per os
infection per os

Browse Nearby Words

peroral
per os
perosis
See all Nearby Words

Cite this Entry

“Per os.” Merriam-Webster.com Medical Dictionary, Merriam-Webster, https://www.merriam-webster.com/medical/per%20os. Accessed 2 Dec. 2025.

Copy Citation

Share

Love words? Need even more definitions?

Subscribe to America's largest dictionary and get thousands more definitions and advanced search—ad free!

Popular in Grammar & Usage

See More

31 Useful Rhetorical Devices

'Affect' vs. 'Effect'

The Difference Between 'i.e.' and 'e.g.'

Why is '-ed' sometimes pronounced at the end of a word?

What’s the difference between ‘cemetery’ and ‘graveyard’?
See More

Popular in Wordplay

See More

Are you in a 'food coma'?

17 Words for Dog Breeds

Words That Turned 100 in 2025

How 'Namaste' Entered The English Language

'Za' and 9 Other Words to Help You Win at SCRABBLE
See More

Popular

See More

31 Useful Rhetorical Devices

Are you in a 'food coma'?

17 Words for Dog Breeds
See More

Games & Quizzes

See All
Play Quordle: Guess all four words in a limited number of tries. Each of your guesses must be a real 5-letter word.
Quordle Can you solve 4 words at once?
Play Blossom: Solve today's spelling word game by finding as many words as you can using just 7 letters. Longer words score more points.
Blossom Pick the best words!
Play Missing Letter: a crossword with a twist. Each of the 25 puzzle words start with a different letter of the alphabet. Which letter is missing?
The Missing Letter A daily crossword with a twist
petit-fours
Name That Dessert! Hope you’ve saved room for some sweet vocabulary.
See All