Meaning & use
a thou
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Meanings
nouncountableinformaltechnical
A thousandth of an inch, used especially in engineering and machining.
Grammar: Countable: one thou, five thou.
Patterns
- a thou of an inch
- measure something in thous
The part must be accurate to within a thou.
The gap is only a few thous wide.
Machinists often work in thous rather than millimeters.
pronounarchaicreligion
An old word for 'you' when speaking to one person, still used in some religious language.
Grammar: Archaic pronoun; used as the subject of a sentence, e.g. 'Thou art kind.'
Patterns
- thou art
- thou shalt
In old prayers, people said 'thou' instead of 'you'.
The word 'thou' appears often in Shakespeare's plays.
Word forms
| plural | thous |
|---|
Common combinations
- within a thou
- The hole must be within a thou of the correct size.
- a few thous
- The surface is flat to a few thous.
- measure in thous
- Engineers often measure in thous.
Synonyms and how they differ
- mil
- Also means a thousandth of an inch in engineering; 'mil' is more common in the US.
Word family
- thousandth noun
- One of a thousand equal parts.
Commonly confused: a thou or thou (pronoun)? a thou or though?
a thou vs thou (pronoun)
The old pronoun meaning 'you'; the engineering 'thou' is a unit of measurement.
a thou vs though
A conjunction meaning 'despite the fact that'; it sounds similar but is a different word.
Practice
In engineering, what does 'a thou' mean?
Choose one answer.
'Thou' in engineering means one thousandth of an inch, not a thousandth of a meter or a sum of money.
Make it your own
Write a sentence using “a thou”, then check it and compare it with the examples above.