只要 vs 如果／要是

[歐博思]

They seem to overlap a bit and I don't quite understand the difference. Usage comments?

[陳德聰]

只要 as long as

如果／要是 if

只要 has a feeling of "all you need to do is..."

It gives a basic requirement for whatever the result you want to get, and as long as you have that one basic requirement, you will definitely get that result. There may be many different ways of achieving said result, but whatever comes after 只要 is presented as a surefire way. It also implies a pretty strong relationship between the antecedent and the consequent, e.g. 课堂只要有美女，男生就愿意上课 where all you have to do to get the male students to come to class is have some pretty girls there.

如果／要是 is just plain "if"

This is the multipurpose "if". If it rains tomorrow, I won't go to class. If I can do it, he can do it too.

[大板牙的兔子]

I think Chen is right about these two phrases.

I'm Chinese. When I do chinese-english translation, I usually translate 只要 into as long as and 如果/要是 into if。

In Chinese， we usually use 只要.......就...... together.

[李婧-Rachel]

hello,I am a Chinese girl.I think maybe you can try this way:Use “只要” the same way as "once",for example:Once you tell me the truth, I will give back your hat.The Chinese meaning is ,只要你告诉我真相，我就把帽子还给你。And for “如果”,the English meaning is"if":If you tell me the truth, I will give back your hat.如果你告诉我真相，我将把帽子还给你。In fact,those two words have the similar meanings, but their tones are different.The former has a more threatened tone,and the latter will be more polite.

[lvn]

只要 expresses a sufficient condition and it can be compared with 只有 (a necessary condition). I don't think it is a good idea to translate 只要 with "Once". Let's have a look at the following example taken from the novel Huozhe 活着 (author: Yu Hua 余华) where Jia Zhen is ready to forgive her husband Fu Gui who has just bankrupted the family if he won't gamble anymore:

 

只要你以后不赌就好了

[lingo-ling]

Just a note: I learned about 要是 in school, but I can probably count on one hand the number of times I've encountered it in real life. (I live in Taiwan.)

[陳德聰]

I think that when they teach 要是, they probably should teach it as "要(是)".

 

I don't think I ever hear "要是" either, but it is routinely used as in "要想皮肤好，粥里加大枣".

[muyongshi]

I hear 要是 used probably on a daily basis (by people other than me). I find it odd that others hear it so infrequently.

I would also disagree that teaching it as 要(是) is appropriate. First because I have never seen support for it in the dictionary and secondly (I would love to hear others thoughts on this as my own opinion is speculation) dropping the 是 is not correct but rather done in situations where flow and balance are desire, ie in an advertisement.

[陳德聰]

I'm thinking of ways to explain why 要 is the part of 要是 that means the "if", and 是 introduces the clause.
 

So far all I've got is 要不然, numerous 要想 examples that are not advertisements, 只要 being followed by a condition... Meh. It's incorrect though. ;)