1. Godan verb with 'su' ending, Transitive verb

   1.

   to increase; to add to; to augment

Example sentences

• 運動量を増やすつもりなんだ。

  I'm going to get more exercise.

• 上級者が英語力（特に読解力）をつけたければ、語彙を増やすのが王道ですね。

  If the more advanced want to improve English ability (especially reading comprehension) increasing vocabulary is the way to go.