tauvsthatWhat's the difference?

Quick tell: tau is a noun, that is a conjunction, so they fill different roles in a sentence.

Which to use

“tau” is a noun and “that” is a conjunction - they look or sound alike but fill different roles in a sentence.

#32,397
“tau” frequency rank
#3,648
“that” frequency rank
36045
confusion score

Side-by-Side Comparison

Feature tau that
Definition nome da décima nona letra do alfabeto grego (Τ/τ) que

Where the eye mixes tau and that

Muted = shared; highlighted = the visual trap. They share 2 letters in sequence.

3 ch
tau
4 ch
that

Why the eye confuses tau with that

These two trip readers on the page rather than in the ear: tau is /taw/ while that is /ðæt/. Spoken aloud the problem disappears. In writing it persists, because they differ by 1 letter(s) in length, and the parts of speech differ too (noun vs conjunction), which is usually the fastest check. Our composite confusion score for this pair is 36045, derived from the frequency rank of both members and their visual similarity.

tau is recorded at frequency rank #32,397, classified as anoun, pronounced /taw/. that is at rank #3,648, tagged as aconj, pronounced /ðæt/.

Glosses for this pair are partially populated in our dataset, but the full side-by-side definitions above should still guide you to the right choice.

With a confusion score of 36045, this pair ranks #30,854 of 75,631 scored Portuguese confusable pairs - roughly mid-pack for confusability.

Orthographic DNA of tau vs that

Shared letters: at. Private to "tau": u. Private to "that": h.

"tau" · 3 letters · shape CVV  ·  "that" · 4 letters · shape CCVC

Known mistypes of this pair

  • thathtat · taht · thatt · thhat · thta · tthat

Frequently Asked Questions

Is swapping "tau" for "that" ever safe?
No - they are not even the same part of speech. "tau" is a noun and "that" a conjunction, so a sentence built for one is usually ungrammatical with the other.
Frequency check: "tau" vs "that" - which ranks higher?
"that" is the more common of the two: it sits at frequency rank #3,648 in our Portuguese list, against #32,397 for "tau". The two are close in frequency, so neither is a safe default; check the meaning rather than guessing.

What to do next

Visual near-miss handled. Browse the word pages or a neighbour when the next look-alike shows up.

  • Full dictionary entry for "tau" with definition, IPA, and generated misspellings. Word entry
  • Full dictionary entry for "that" - compare definitions side by side with the headword page. Word entry
  • This pair ranks #30,854 of 75,631 scored Portuguese confusable pairs in this corpus vintage. Corpus statistics
  • "tau" and "that" also get mixed up with nearby pairs, the highest-scored neighbour is "tau vs til". Nearby pair
  • Recorded mistypes exist for at least one side of this pair, useful when a spell-checker or OCR lands on the wrong form. See mistypes

Confusion rank #30,854 of 75,631 scored Portuguese pairs, corpus vintage 2026-09-03, not spelling advice.

Source: Wiktionary (via kaikki.org) Structured Wiktionary extract

Source: FrequencyWords open word-frequency list