certovscésioWhich spelling fits?

Quick tell: certo is a adjective, césio is a noun, so they fill different roles in a sentence.

Which to use

“certo” is an adjective and “césio” is a noun - they look or sound alike but fill different roles in a sentence.

#326
“certo” frequency rank
#41,427
“césio” frequency rank
41753
confusion score

Side-by-Side Comparison

Feature certo césio
Definition verdadeiro, evidente elemento químico de símbolo Cs, possui o número atômico 55 e massa atômica relativa 132,905 u; é um metal alcalino, de coloração ouro prateado; é encontrado em minerais de potássio, tais como micas, berílio, feldspatos e a polucita (alumínio-silicato de césio); o césio metálico é utilizado na fabricação de células fotoelétricas e detectores de infravermelho

Where the eye mixes certo and césio

Muted = shared; highlighted = the visual trap. They share 2 letters in sequence. certo (CVCCV) and césio (CVCVV) run the same length but a different consonant-vowel pattern - the shape difference is usually the fastest tell.

5 ch
certo
5 ch
césio

Look-alike desk: certo vs césio

These two trip readers on the page rather than in the ear: certo is /ˈsɛɹ.tʊ/ while césio is /ˈsɛzju/. Spoken aloud the problem disappears. In writing it persists, because they share most of their letters but differ in 3 positions, and the parts of speech differ too (adjective vs noun), which is usually the fastest check. Our composite confusion score for this pair is 41753, derived from the frequency rank of both members and their visual similarity.

certo is recorded at frequency rank #326, classified as anadj, pronounced /ˈsɛɹ.tʊ/. césio is at rank #41,427, tagged as anoun, pronounced /ˈsɛzju/.

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 41753, this pair ranks #24,126 of 75,631 scored Portuguese confusable pairs - roughly mid-pack for confusability.

Orthographic DNA of certo vs césio

Shared letters: co. Private to "certo": ert. Private to "césio": isé.

"certo" · 5 letters · shape CVCCV  ·  "césio" · 5 letters · shape CVCVV

Known mistypes of this pair

  • certo ← ccerto · cerot · cerrto · certto · cetro · creto · ecrto

Frequently Asked Questions

Is swapping "certo" for "césio" ever safe?
No - they are not even the same part of speech. "certo" is an adjective and "césio" a noun, so a sentence built for one is usually ungrammatical with the other.
Frequency check: "certo" vs "césio" - which ranks higher?
"certo" is the more common of the two: it sits at frequency rank #326 in our Portuguese list, against #41,427 for "césio". That is a wide gap, so in ordinary text the rarer spelling is the one worth double-checking.

Useful next steps

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

  • Full dictionary entry for "certo" with definition, IPA, and generated misspellings. Word entry
  • Full dictionary entry for "césio" - compare definitions side by side with the headword page. Word entry
  • This pair ranks #24,126 of 75,631 scored Portuguese confusable pairs in this corpus vintage. Corpus statistics
  • "certo" and "césio" also get mixed up with nearby pairs, the highest-scored neighbour is "césio vs cisto". 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 #24,126 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