underline

Etymology

It is formed from English under- + line,^{[2][3][4][5][6]} with the verb in the sense "to mark with a line".^[2][4] The OED and Etymonline compare Dutch onderlijnen.^[2][3] The noun, from 1886, is formed in the same way from the noun.^[2][7]

Earliest recorded meaning

To mark words with a line or lines drawn underneath: 1721, in J. Strype's Ecclesiastical Memorials.^[2][3] Merriam-Webster Unabridged gives the same year;^[4] the Shorter Oxford dates the verb to the mid 16th century.^[7]

Semantic evolution

Johnson (1755) defined the verb as marking words with lines beneath them, with a quotation from Wotton.^[6] In the theatre it was used from 1825 for announcing a play by a line at the foot of a playbill.^[2] The figurative sense "to emphasize", especially in speech, is recorded from 1880, from the use of underlining to stress written words.^[2] The noun appeared in the 1880s, for the line of the underside of an animal's body (1886), a line drawn under words, guiding lines laid under writing paper (1888) and a playbill's announcement of the next piece (1891); a caption beneath a picture followed in 1924.^[2][4][3]

Timeline

• 1721 – to mark words with a line drawn beneath.^[2][3][4]
• 1825 – to announce a play by a line at the foot of a playbill.^[2]
• 1880 – figurative, to emphasize, especially in speech.^[2]
• 1886 – noun, a line drawn under something.^[4] Etymonline dates the noun to 1888.^[3]
• 1886 – noun, the line of the lower part of an animal's body.^[2]
• 1888 – noun, in the plural, ruled guiding lines placed under writing paper.^[2]
• 1891 – noun, a line at the foot of a playbill announcing the next piece.^[2]
• 1924 – noun, a caption beneath a picture.^[2]

Meanings

Verb

1. To draw a line under a word or passage; to underscore: She underlined the key dates in red.^[8][4][2]
2. To emphasize or make clear the importance of something: The breakdown underlined the need for spare parts.^[8][4][2]

Noun

1. A line drawn under written or printed words.^[8][4][7]
2. A caption or legend beneath an illustration.^[4][2]
3. In the plural, a set of guiding lines placed under a sheet that is being written on.^[4][2]
4. A line at the foot of a playbill announcing a coming performance.^[4][2]
5. The line of the underside of an animal's body.^[2][7]

Word family

• underliner
• underlining

Related words

• underscore
• line

Usage notes

The OED and Merriam-Webster Unabridged also have an older verb underline, "to furnish with an underlining", that is, to put a lining under something, recorded from 1545 and formed from under- and the verb line "to cover the inner surface".^[2][4][7]

References

1. ^ a b Wiktionary, the free dictionary, https://en.wiktionary.org
2. ^ a b c d e f g h i j k l m n o p q r s t u v Oxford English Dictionary Online (accessed March 2026), Oxford: Oxford University Press
3. ^ a b c d e f Harper, Douglas. Online Etymology Dictionary, https://www.etymonline.com
4. ^ a b c d e f g h i j k l m Merriam-Webster Unabridged Dictionary (2024), online ed., Springfield, Mass.: Merriam-Webster
5. ^ Dictionary.com Unabridged (2016), based on the Random House Unabridged Dictionary, New York: Random House
6. ^ a b Johnson, Samuel (1755), A Dictionary of the English Language, London; 4th ed. 1773; Johnson's Dictionary Online, ed. Beth Rapp Young et al.
7. ^ a b c d e Shorter Oxford English Dictionary on Historical Principles (2002), 5th ed., ed. William R. Trumble and Angus Stevenson, Oxford: Oxford University Press
8. ^ a b c Collins English Dictionary (2023), Glasgow: HarperCollins