くわkuwaえるeru
1.

To introduce a new element or feature to something that already exists, enhancing its overall composition or unity.

2.

To take action that improves a situation by addressing previous inadequacies or deficiencies.

3.

To intensify or amplify something, resulting in a significant increase in its degree or impact.

4.

To invite someone or something to join a group or team, thereby expanding its membership or participation.

5.

To exert influence or impact through an action directed towards another party, often resulting in a change or effect.

Example:

水を加えてペースト状になるまでかき回しなさい。

tsukeくわkuwaえるeruつけtsukeくわkuwaえるeru
1.

To annex or supplement something that already exists by introducing an additional component or detail.

2.

To enhance or expand upon an existing item or idea by appending something new.

Example:

リストに彼の名前をつけ加えた。

tsukeくわkuwaえるとeruto
1.

A phrase used to introduce supplementary information or an additional thought to what has already been stated.

2.

An expression that indicates an extra point or clarification that expands upon the previous statement.