oncost

noun

By · According to Wiktionary data (CC BY-SA) ·

"oncost" is a 6-letter English headword indexed on PlainSpell.

The verdict

“oncost” is uncommon English (outside the top frequency list), classed as a noun. The kind of spelling people second-guess.

Unranked
below top-frequency English
6
letters

According to Wiktionary data (CC BY-SA, analyzed May 6, 2026) - Additional costs; extra expenses.

Key facts for oncost
PropertyValue
Headwordoncost
LanguageEnglish
Part of speechNoun
Letters6
Misspellings tracked0
Confusable pairs0
SourceWiktionary (kaikki.org)

Where “oncost” sits in English frequency

oncost falls outside the top-100,000 ranked English words, the long-tail zone of technical, archaic, or low-frequency vocabulary, exactly where readers second-guess spellings most.

Beyond rank #100,000. Source: FrequencyWords open word-frequency list.

Rare enough to double-check

oncost is uncommon English outside the top frequency list, classed as anoun. Rarity is why readers land here mid-draft. 4 senses are on record.

Zero misspellings are on record for oncost in our index, since its letter sequence doesn't invite the usual edit-distance slips. Our confusable-pair dataset has no match for it, since its spelling is unusual enough that it doesn't cluster with a lookalike.

Etymologically, the entry records: From on- + cost, or from Middle English uncost (“additional expense”), from Middle Dutch oncost (“expenses, overhead”) (Modern Dutch onkost), equivalent to un- + cost. Cognate with German Unkost (“expenses”). The correct English form is oncost, spelled O-N-C-O-S-T.

Definition

  1. 1
    Additional costs; extra expenses.
  2. 2
    Overhead (expense)
  3. 3
    The cost of upkeep, making and maintaining shafts, roads, pumping, etc.
  4. 4
    The indirect expenditure incurred for the purpose of increasing the productive power of organised labour.

Etymology

From on- + cost, or from Middle English uncost (“additional expense”), from Middle Dutch oncost (“expenses, overhead”) (Modern Dutch onkost), equivalent to un- + cost. Cognate with German Unkost (“expenses”).

Definitions, pronunciation, and etymology for this entry are drawn from Wiktionary via the kaikki.org structured extract (CC BY-SA). See the methodology for how each field is sourced and updated.

Frequently Asked Questions

How do you spell "oncost"?
"oncost" is spelled O-N-C-O-S-T.
What does "oncost" mean?
As a noun, "oncost" means: Additional costs; extra expenses.
What is the origin of the word "oncost"?
From on- + cost, or from Middle English uncost (“additional expense”), from Middle Dutch oncost (“expenses, overhead”) (Modern Dutch onkost), equivalent to un- + cost. Cognate with German Unkost (“expenses”). See the full etymology section above for more details.
Is PlainSpell free to use?
Yes, PlainSpell is a completely free word reference. You can look up definitions, pronunciations, confusable pairs, homophones, and spelling corrections across 5 languages without any sign-up or subscription.

Using “oncost”

The practical upshot for anyone who landed here from a spell-check.

  • The one correct English spelling is O-N-C-O-S-T - every other letter order is a misspelling in standard orthography.
  • Browse more English words and confusable pairs in the same reference. English words
Data Source

Wiktionary (via kaikki.org), licensed under CC BY-SA & GFDL. Word ordering uses an open word-frequency list; misspelling variants are generated by edit-distance from the correct headword.

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

Source: FrequencyWords open word-frequency list FrequencyWords open word-frequency list