It's the dictionary form look it up!
Can be backformed from masu.
drop ます
go from い row to う row for v5 (group1) いきます → いく
add る for v1 (group2) みます→ みる
Knowing both the dic-form and the masu-form should clarify verb groups.
eg.
おきます → おきる → to get up v1 (group2)
おきます → おく→ to press v5 (group1)
This is essentially why you should start from the dictionary form, knowing the group and if a verb is transitive or intransitive.
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