deleterious
/ˌdɛ.ləˈtɪɹ.i.əs/adjective
deleterious is spelled D-E-L-E-T-E-R-I-O-U-S: 11 letters and 5 syllables. It appears about once in every 2 million words in written English, the 40,703rd most frequent word form (wordfreq, 2021 data). As an adjective, deleterious means “Harmful, often in a subtle or unexpected way” (English Wiktionary, September 2026).
How many letters and syllables are in deleterious?
| Letters | 11: D-E-L-E-T-E-R-I-O-U-S |
|---|---|
| Syllables | 5 (from its American pronunciation) |
| In writing | about once in every 2 million words; the 40,703rd most frequent word form |
| Wrong spellings searched | none measured in search |
| Rhymes with |
Sources: letters and syllables from the English Wiktionary's hyphenation or pronunciation and the CMU Pronouncing Dictionary; written frequency: wordfreq 3.1 (a 2021 snapshot of Wikipedia, subtitles, news, books, web text and social media); rhymes and same-letter words are computed by PlainSpell from its own word list.
How common is deleterious?
Deleterious appears about once in every 2 million words in written English, the 40,703rd most frequent word form in the list.
Source: written frequency: wordfreq 3.1 (a 2021 snapshot of Wikipedia, subtitles, news, books, web text and social media).
How do you pronounce deleterious?
- UK /ˌdɛl.ɪˈtɪə̯.ɹi.əs/
- UK /ˌdɪl.ɪˈtɪə̯.ɹi.əs/
- US /ˌdɛ.ləˈtɪɹ.i.əs/
Deleterious has 5 syllables (counted from its American pronunciation in the CMU Pronouncing Dictionary).
Source: English Wiktionary, dump of September 2, 2026 (CC BY-SA 4.0), through kaikki.org (Wiktextract). Recordings: En-us-deleterious.ogg, En-au-deleterious.ogg, Wikimedia Commons (author and licence on each file's page).
What rhymes with deleterious?
2 words on PlainSpell end in the same sounds as deleterious from its last stressed vowel (/ɪɹiəs/):
Computed by PlainSpell from the pronunciations in the English Wiktionary (dump of September 2, 2026): a rhyme shares every sound from the last stressed vowel to the end; ordered by written frequency (wordfreq 3.1).
Forms of deleterious
- more deleterious comparative
- most deleterious superlative
- deletorious
Source: English Wiktionary, dump of September 2, 2026 (CC BY-SA 4.0), through kaikki.org (Wiktextract).
What does deleterious mean?
The meanings the English Wiktionary records, quoted as written there (source below).
adjective
- 1
Harmful, often in a subtle or unexpected way.
deleterious effects
- 2
Having lower fitness.
A deleterious mutation
Source: English Wiktionary, dump of September 2, 2026 (CC BY-SA 4.0), through kaikki.org (Wiktextract).
Deleterious in Spanish, French, German and Portuguese
In the sense harmful:
| Language | Words |
|---|---|
| French | délétère |
| German | schädlich, gesundheitsschädlich |
| Portuguese | deletério |
| Spanish | deletéreo |
Source: English Wiktionary, dump of September 2, 2026 (CC BY-SA 4.0), through kaikki.org (Wiktextract). Translations are Wiktionary's, by sense; a linked word has its own PlainSpell page.
Where does deleterious come from?
Adapted borrowing (1640s; 1582 as deletorious) of New Latin dēlētērius, dēlētōrius + -ous, from Ancient Greek δηλητήριος (dēlētḗrios, “noxious, deleterious”), from δηλητήρ (dēlētḗr, “a destroyer”), from δηλέομαι (dēléomai, “I hurt, damage, spoil, waste”). Not related to delete or deleble. Doublet of deletery.
Source: English Wiktionary, dump of September 2, 2026 (CC BY-SA 4.0), through kaikki.org (Wiktextract).