is vs ISS, What's the Difference?

Which to use

“is” is a verb and “ISS” is a name - they look or sound alike but fill different roles in a sentence.

#8
“is” frequency rank: #16,055
“ISS” frequency rank: 16063
confusion score

Side-by-Side Comparison

Feature	is	ISS
Definition	third-person singular simple present indicative of be	Initialism of International Space Station.

Letter map: is vs ISS

Shared letters muted; letters that set is and ISS apart highlighted. Shared run: 2.

2 ch

3 ch

ISS

Part-of-speech tell for is / ISS

Our dataset has no pronunciation recorded for both members, so the reliable separator here is grammatical: is is averb and ISSaname. On the page they differ by 1 extra letter(s) - “is” sits inside “ISS”. Our composite confusion score for this pair is 16063, derived from the frequency rank of both members and their visual similarity.

is is recorded at frequency rank #8, classified as averb, pronounced /ɪz/. ISS is at rank #16,055, tagged as aname.

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 16063, this pair ranks #460,160 of 530,003 scored English confusable pairs - a relatively easy-to-tell-apart pair.

Orthographic DNA of is vs ISS

Shared letters: is. Private to "is": -. Private to "ISS": -.

"is" · 2 letters · shape VC · "ISS" · 3 letters · shape VCC

Frequently Asked Questions

Is swapping "is" for "ISS" ever safe?

No - they are not even the same part of speech. "is" is a verb and "ISS" a name, so a sentence built for one is usually ungrammatical with the other.

In ordinary English text, does "is" or "ISS" show up more?

"is" is the more common of the two: it sits at frequency rank #8 in our English list, against #16,055 for "ISS". That is a wide gap, so in ordinary text the rarer spelling is the one worth double-checking.

What to do next

Done with this confusable. These links stay specific to "is" and "ISS".

Full dictionary entry for "is" with definition, IPA, and generated misspellings. Word entry
Full dictionary entry for "ISS" - compare definitions side by side with the headword page. Word entry
This pair ranks #460,160 of 530,003 scored English confusable pairs in this corpus vintage. Corpus statistics
"is" and "ISS" also get mixed up with nearby pairs, the highest-scored neighbour is "ISS vs ith". Nearby pair

Confusion rank #460,160 of 530,003 scored English pairs, corpus vintage 2026-09-03, not spelling advice.