When to use っ and つ (for 五つ and 六つ Things Reading Exercises)

Could somebody please help me understand why 五つ is written as いつつ (regular tsu) and 六つ is written as むっつ (small tsu) in reading exercises?

Both are numerals that have a hiragana attached to them and have kun’yomi reading of the kanji, but is there any rule I must know when typing it?

I’m getting very confused.


When a word is written with a normal sized つ, such as in いつつ. Its pronounced and written the way it looks. In romaji, this would be “itsutsu”. When a word is written with a small tsu っ, such as in むっつ, it’s actually an indicator that the consonant sound following it is doubled. So, this would be written “muttsu”. When pronouncing it, small っ is silent but still takes up one beat of time in the word. So where むつ is a 2 beat word, むっつ is a 3 beat word pronounced |む|Silence|つ|. I hope that helps!


Counters have a lot of irregularities, unfortunately. You aren’t missing a rule or anything like that - you just have to memorize that five things is pronounced いつつ and six things is pronounced むっつ.


It’s not quite silence. You need to form and hold the “ts-” consonant shape with your mouth, before releasing it on the next beat. To use the linguistics terms, it’s gemination rather than a glottal stop. (Small っ can function as a glottal stop in specific situations, but this is not it.)


The difference between the big and small つ is already explained above. As for the why, the small っ seems to serve as a marker that a sound was once there but is now omitted, similar to the ’ in English. Since 六日 is pronounced むいか, you would expect 六つ to be pronounced むいつ, but the い got dropped for one reason or the other and in these situations the dropped sound is often replaced with っ.


(This is a historical digression, not really important to understanding modern Japanese.)

I think that both むいか and むっつ are not the “original” form. In Old Japanese, it was almost never the case that two vowels were together in a word, as they are in むいか (u-i); the language was almost purely CVCVCV, with the vowel-only syllables あいうえお almost always at the start of words only. The sound changes (“onbin”) that arrived with the change from Old Japanese to Early Middle Japanese about a thousand years ago could reduce a CV syllable to a vowel, to an ん nasal, or to the “long consonant” now written with the small-tsu っ[*], and you don’t get word forms like either むいか or むっつ before then. 六日 and 六つ happened to end up taking different routes. Wikipedia thinks the original OJ stem for 6 was just “mu”, so maybe “muka” and “mutu” is where they started?

[*] You can see this in the way verbs inflect for their te forms: よむ : よんで, かく : かいて and わかる : わかって were all originally the more regular looking よみて かきて わかりて, but the reduction of their syllables went down different paths.