One of English's quietest grammar tricks is hiding in plain sight: take a noun, voice the final fricative, and you get a verb. Bath (a tub) becomes bathe (to wash). Use (a noun, /juːs/) becomes use (a verb, /juːz/). Same spelling sometimes; new sound. This rule is responsible for dozens of word pairs that English speakers learn intuitively but second-language learners trip on.
The Rule
When a noun ending in a voiceless fricative is converted to a verb, the fricative becomes voiced:
- /θ/ (TH) → /ð/ (TH): bath → bathe, breath → breathe, cloth → clothe.
- /s/ → /z/: use → use, abuse → abuse, house → house, advice → advise (also a spelling change).
- /f/ → /v/: belief → believe, half → halve, life → live (also spelling change).
In some pairs the spelling stays the same and only the sound changes. In others, the spelling changes too (TH → THE, F → V, ICE → ISE).
TH Pairs Practice
Notice the vowel often lengthens too: bath /æ/ → bathe /eɪ/, breath /ɛ/ → breathe /iː/, cloth /ɔ/ → clothe /oʊ/.
S/Z Pairs Practice
F/V Pairs Practice
Why Did English Develop This Pattern?
This pattern is a fossil from Old English. The verb form originally had a suffix (-ian) that placed the fricative between vowels, where it naturally voiced. The suffix later disappeared, but the voicing stuck. So the pronunciation difference preserves a grammatical fact that the spelling has lost.
The Spelling Cue: Watch for Final E
For TH and S, the verb often adds a final E: bath → bathe, cloth → clothe, advice → advise. The E doesn't make a sound; it signals voicing of the previous fricative. So:
- bath (no E) = /θ/, noun.
- bathe (with E) = /ð/, verb.
- advice (no E) = /s/, noun.
- advise (S+E) = /z/, verb.
For F → V, the spelling sometimes changes (half → halve), sometimes stays the same (belief vs believe shows F → V plus E added).
Identical-Spelling Pairs (Sound Only)
The trickiest pairs have no spelling change. You need context:
- house /haʊs/ (noun) vs house /haʊz/ (verb)
- use /juːs/ (noun) vs use /juːz/ (verb)
- abuse /əˈbjuːs/ (noun) vs abuse /əˈbjuːz/ (verb)
- excuse /ɪkˈskjuːs/ (noun) vs excuse /ɪkˈskjuːz/ (verb)
- close /kloʊs/ (adj) vs close /kloʊz/ (verb)
Native speakers do this distinction automatically. If you don't, you might say I houss them instead of I house them, which sounds non-native immediately.
Exceptions and Words That Don't Follow the Rule
- death (noun) → no verb. To die comes from a different root.
- worth stays /θ/ in both noun and adjective uses (no verb form).
- truth stays /θ/ — no verb in modern English (the obsolete truthe /truːð/ disappeared).
Practice Sentences
- I take a bath every Sunday and I bathe the dog on Mondays.
- Take a deep breath; breathe slowly.
- The use of plastic is high; many companies do not use recycled materials.
- That is a close call. Please close the window.
Quick Summary
Noun = voiceless fricative (s, f, θ). Verb = voiced fricative (z, v, ð). The spelling sometimes signals it (with -e or letter change), sometimes doesn't. Master this pattern and you instantly upgrade dozens of high-frequency word pairs.