Ulterior almost always appears in one fixed phrase: an ulterior motive. That means a hidden reason for doing something — the real reason, kept out of sight, usually because it benefits you.

Ulterior Ulterior almost always appears in one fixed phrase幾乎只出現在一個固定片語裡: an ulterior motive an ulterior motive（別有用心的動機）。That那 means a hidden reason for doing something意思是做某件事背後藏著的理由 — the real reason, kept out of sight那個真正的原因被藏起來, usually because it benefits you通常是因為對自己有好處。

Someone helps you move house and you later find out they wanted a look at your flat: that is an ulterior motive. The key is not just hidden but self-serving; a nice surprise kept secret is not an ulterior motive.

Someone helps you move house and you later find out they wanted a look at your flat有人幫你搬家，後來你才發現他其實只是想看看你家的公寓: that這 is an ulterior motive就是an ulterior motive（別有用心的動機）。The key重點 is not just hidden but self-serving不只是「藏起來」，還要「對自己有利」; a nice surprise kept secret一個被保密的美好驚喜 is not an ulterior motive並不算ulterior motive。

The word is nearly always negative, and it nearly always comes before 'motive', sometimes 'purpose' or 'design'. You cannot say 'his reason was ulterior' — it does not sit after 'be' in normal English. Note the plural sounds natural too: 'I think she had ulterior motives'.

The word這個字 is nearly always negative幾乎總是負面的, and而且 it nearly always comes before 'motive', sometimes 'purpose' or 'design'幾乎總是放在「motive」前面，有時候也放在「purpose」或「design」前面。You你 cannot say 'his reason was ulterior'不能說「his reason was ulterior」 — it它 does not sit after 'be' in normal English在一般英文裡不會放在be動詞後面。Note the plural sounds natural too要注意複數也很自然: 'I think she had ulterior motives'「I think she had ulterior motives我覺得她另有企圖」。

There is a second, much rarer meaning — 'further away' or 'beyond', or 'coming later' — which you will meet only in old legal or formal writing. Ignore it for speaking; recognise it if you see it.

There is a second, much rarer meaning還有第二個、少見得多的意思 — 'further away' or 'beyond', or 'coming later'「更遠的」、「更後面的」，或是「稍後才來的」 — which you你 will meet only in old legal or formal writing只會在老式的法律或正式文書裡遇到。Ignore it for speaking說話時可以不用管它; recognise it if you see it看到的時候能認出來就好。

And be careful of the spelling: it ends -ior, like superior and inferior, not -ier.

And還要 be careful of the spelling注意拼法: it它 ends -ior, like superior and inferior字尾是-ior，跟superior、inferior一樣, not而不是 -ier -ier。