The three verb groups

Every Japanese verb in its dictionary form ends in a kana from the u row of the syllabary — う, く, ぐ, す, つ, ぬ, ぶ, む or る — and every verb belongs to one of three groups. The group decides how all the other forms are built, so it is the first thing to know about a new verb, in the same way that an English speaker needs to know that "go" is irregular before saying "went".

The う-verbs (also called group 1 or godan verbs) keep a root and change their last kana: 書(か)く becomes 書(か)きます, 書(か)かない, 書(か)こう. The る-verbs (group 2 or ichidan verbs) drop the final る and add an ending to what is left: 食(た)べる becomes 食(た)べます, 食(た)べない. The irregular group has two members, する "to do" and 来(く)る "to come" — plus the hundreds of verbs built on する, such as 勉強(べんきょう)する "to study". In the table, the first colour is the part that stays and the second the part that changes or drops; the irregular part has a colour of its own.

Telling them apart takes two questions. A verb that does not end in る is always a う-verb. A verb ending in る after an a, u or o sound — 分(わ)かる, 作(つく)る, 乗(の)る — is a う-verb too, apart from the two irregulars する and 来(く)る. Only a verb ending in -iru or -eru can be a る-verb: 見(み)る, 起(お)きる, 寝(ね)る, 食(た)べる. Most of them are — but not all.

The ones that are not are where English speakers go wrong. 帰(かえ)る "to go home", 入(はい)る "to enter", 走(はし)る "to run", 知(し)る "to know" and 切(き)る "to cut" look exactly like る-verbs and are う-verbs, so their ます-form keeps the り: 帰(かえ)ります. The common ones fit on a single card, and learning them as a list is quicker than meeting them one mistake at a time.