Tricky uses of "dao"
You probably learned the result complement 到 a long time ago, as part of words like 看到 ("to see") and 听到 ("to hear"). But other times it's less clear what the 到 really means. Like the difference between 买 and 买到 or 做 and 做到. What 到 adds is a clearer sense that something has really been achieved.
The difference 到 makes
Adding 到 after a verb makes it very clear that the desired result was achieved. If you looked and you saw, then 到 indicates that. On the other hand, not adding 到 makes it unclear whether or not the desired result was achieved. It can have the effect of making a verb mean "try to verb." So 做 without 到 is kind of like "try to do," but when you want to make it very clear that results were achieved or must be achieved, that's when you want to add 到.
Let's look at another example. The difference between 找 and 找到 is that 找 means "to search" (in other words, "to try to find"), whereas 找到 means "to find," that the search was successful, and results were achieved. So if one were to say "你一定要找," it would mean "you must try to find it" and "你一定要找到" means "you must find it."
做 vs. 做到
- 我 还 没有 做。I haven‘t done it.
- 我 下 个 星期 可以 做。I can do it next week.
- 我 相信 你 一定 能 做到。I believe you will be able to do it.
买 vs. 买到
- 我 还 没有 买 。I haven't bought it yet.
- 我 没 买到 。I didn't buy it.
- 这里 买 不 到 进口 食品 。You can't buy imported good here.
学 vs. 学到
- 我 想 学 中文 。I want to study Chinese.
- 我们 今天 学 了 很 多 生词 。Today we learned many new words.
- 在 这个 公司 工作 ，我 学到 了 很 多 东西。Working for this company, I learned a lot of things.
拿 vs. 拿到
- 你 拿 小包 ，我 拿 大包 。You take the small bag, I'll take the big bag.
- 不 知道 什么 时候 能 拿到 我 的 工作 签证 。I'm not sure when I'll be able to get my work visa.
- 如果 他 拿 不 到 绿卡 ，我 就 跟 他 分手 。If he can't get a green card, I will break up with him.
想 vs. 想到
- 一定 要 想 一 个办法 。You have to think of a method.
- 你 想到 了 什么好办法 ？Have you thought of any good methods yet?
- 我们 都 没 想到 他 这么 生气 。None of us thought that he would be so mad.
看 vs. 看到
- 我 在 看 一些 老 照片 。I'm looking at some old photos.
- 看到 这 张 照片 ，我 想到 了 我 的 女儿 。After seeing this photo, I thought of my daughter.
- 我 看到 他 了，在 那里 ！I see him, over there!
追 vs. 追到
- 怎么 追 女孩子 ？How do you chase girls?
- 那 个 女孩子 ，你 追到了吗 ？ That girl, did you catch her yet?
- 如果 你 追到她了 ，我 就 请 你 喝酒 。If you can really catch her, I'll treat you to a drink.
了解 vs. 了解到
- 我 不 太 了解 这个 人 。I don't really understand this person.
- 我们 刚刚 了解到 一些 新 的 消息 。We just understood the new information.
- 从 他 那里，我 了解 到 了 真相 。I learned the truth from him.
联系 vs. 联系到
- 我们 怎么 联系 ？How do we get in contact?
- 你 知道 他 的 联系 方式 吗 ？Do you have his contact information?
- 我 想 跟 你 联系 ，但是 一直 联系 不 到 你 。I always wanted to get in touch with you, but hasn't got a hold of you.