What does it mean when a number is followed by こ


> れいぞうこ の なか に ケーキ は 3こ ありました.
>
> せんしゅう 、かんじ を 20こ おぼえ ました.

In the above examples, why does こ come after the number? Is it a counter? If
yes, at what instances can it be used? If not, please advise how and when it
should be used.




The こ is indeed a counter, usually written 個.

It is a _general_ counter for counting objects, much like つ. Your two example
sentences provide proof of the generality of 個, since cakes and kanji
characters have few common features.

つ is often taught as the "default" counter ("default" meaning that it can be
used in practically any situation to make yourself understood). But つ is only
used up to 10 objects. For 11 or more objects, 個 could be regarded as the
default counter.

