The causative form is a special conjugation form for Japanese verbs, which is used to indicate that the subject was coerced or made to perform an action. This is another conjugation form which creates expressions which are accomplished via multiple words working together in English.
Japanese Verb Groups
There are three verb groups in the Japanese language, and the formation of the causative form will depend upon to which group a particular verb belongs. Group one verbs consist of all verbs which do not end in る as well as various verbs ending in る which follow group one conjugation patterns. Group two verbs consist of various verbs which end in る which do not follow group one conjugation patterns and most conjugations/suffixes are added by simply dropping the る ending. Group three consists only of the two irregular verbs in the Japanese language, する (suru) - (to do) and 来る (kuru) - (to come).
Verb Group One Conjugation Rules
The causative form is formed from a group one verb's negative stem, then the ending せる is added. A group one verb's negative stem is formed by replacing its infinitive 'u' ending hiragana syllable with its corresponding 'a' ending hiragana syllable:
ぐ (gu) - が (ga)
む (mu) - ま (ma)
ぶ (bu) - ば (ba)
う (u) - わ (wa) - (exception, わ instead of あ)
働く (hataraku) - (to work)
読む (yomu) - (to read)
飲む (nomu) - (to drink)
働かせる (hatarakaseru) - (made to work)
読ませる (yomaseru) - (made to read)
飲ませる (nomaseru) - (made to drink)
買う (kau) - (to buy)
走る (hashiru) - (to run)
立つ (tatsu) - (to stand)
買わせる (kawaseru) - (made to buy)
走らせる (hashiraseru) - (made to run)
立たせる (tataseru) - (made to stand)
Verb Group Two Conjugation Rules
To conjugate a group two verb into its respective causative form, simply replace the る ending with させる (saseru).
食べる (taberu) - (to eat)
起きる (okiru) - (to wake up)
信じる (shinjiru) - (to believe)
食べさせる (tabesaseru) - (made to eat)
起きさせる (okisaseru) - (made to wake up)
信じさせる (shinjisaseru) - (made to believe)
Verb Group Three Conjugation Rules
The third verb group only includes the two irregular verbs する and くる.
来る (kuru) - (to come)
させる (saseru) - (made to do)
来させる (kosaseru) - (made to come)
Extended Conjugation/Suffixing Rule
When a verb is conjugated into its causative form, it takes on a る ending and any further conjugations/suffixes will follow the group two verb conjugation rule:
食べさせる (tabesaseru) - (made to eat) 食べさせました (tabesasemashita) - (was made to eat)
書かせる (kakaseru) - (made to write) 書かせれば (kakasereba) - (literal - if made to write)
泳ぐ (oyogu) - (made to swim)) 泳がせない (oyogasenai) - (not made to swim)
Usage and Example Sentences
A causative form verb indicates that the action in question was externally made to be or coerced by a third party. The most direct translations of the causative form into English is 'made to'. The coercive subject is often marked with the が particle and the coerced subject is often worked with the particle に.
母が僕に宿題をさせた (haha ga boku ni syukudai wo saseta) - (I was made to do [my] homework by my mother/My mother made me do [my] homework).
コーチがサッカー選手にたくさん運動させました (koochi ga sakkaa sensyu ni takusan undou sasemashita) - (The coach made the soccer players exercise a lot.)
旅券は見せさせませんでした (ryoken wa misesasemasendeshita) - (I was not made to show my passport).
毎日働かせます - (mainichi hatarakasemasu) (I am made to work every day).
A causative verb expression can also be translated to 'let' in a permissive context:
うちの息子にこの本を読ませました (Uchi no musuko ni kono hon wo yomasemashita) - (I let my son read this book.)