了 (le) does not indicate past tense

That 了 (le) is the indicator of past tense is a widespread mistake that many Chinese learners make. The trouble is that many Chinese teachers taught them so. 

This wrong conclusion is due to the following translations from Chinese to English:

• 我昨天看了电影。( wǒ zuó tiān kàn le diàn yǐng.)

I watched a movie yesterday.

• 我今天早上去了健身中心。(wǒ jīn tiān zǎo shang qù le jiàn shēn zhōng xīn.)

I went to the gym this morning.

These translations are accurate, and that gives the connection between 了 (le) and past tense.

Problems come when students want to say “I was at home yesterday” or “Last year I lived in Hong Kong”. They will try to say something like these:

• 我昨天在了家。(wǒ zuó tiān zài le jiā.)
• 去年我住了在香港。(qù nián wǒ zhù le zài xiāng gǎng.)

Unfortunately, both sentences are wrong.

The reason is that 了 (le) is mistaken for past tense. In fact, Chinese does not have past tense. There are no tenses in Chinese.

The function of 了 (le) in a sentence is to tell us the action is completed or there is a change of status regardless whether or not this action happens in the past, at the present or in the future.

For example:

• 我昨天看了电影。 (wǒ zuó tiān kàn le diàn yǐng.)

I watched a movie yesterday. 

The action 看 (kàn) is completed in the past.

• 现在开始上课了。(xiàn zài kāi shǐ shàng kè le.)

Now the class begins. 

The status is changed from the free time earlier to the class time now. 

• 你胖了。(nǐ pàng le.)

You have gained weight. 

The status is changed from a skinnier person before to a heavier person now. 

• 你明天到了就给我打电话。(Nǐ míng tiān dào le jiù gěi wǒ dǎ diàn huà.)

Call me when you get here tomorrow. 

The action 到 (dào) is perceived to be completed in the future.

Many students are confused when sometimes 了 (le) appears after the action and sometimes at the end of the sentence. 

Actually, both are accepted in most cases. 

For example the following two sentences. Both of them are saying the same thing:

• After the action 看 (kàn)

我昨天看了电影。 (wǒ zuó tiān kàn le diàn yǐng.)

• At the end of the sentence

我昨天看电影了。 (wǒ zuó tiān kàn diàn yǐng le.)

When we are expressing a fact, not a change of status or a completed action, do not use 了 (le).

For example:

• 我昨天在家。(wǒ zuó tiān zài jiā.)

I was at home yesterday.

• 去年我住在香港。(qù nián wǒ zhù zài xiāng gǎng.)

Last year I lived in Hong Kong.

• 他说他是中国人。 (tā shuō tā shì zhōng guó rén.)

He said he was Chinese.

了 (le) has many different functions. For example, in fixed structures, such as “要 (yào) ... 了 (le)”, at the end of a sentence as an exclaimer, and many others.

In fact, there are people who wrote PhD theses on the usages of 了 (le). It shows how important 了 (le) is in Chinese. It also tells us that, unless you want to do a PhD, there is no need to spend too much time to think about it. 

It is much better to read more Chinese stories and to enjoy learning Chinese.

Explain the meaning of the sentence with 了 (le), and the one without it.

1. 他有钱了。 (tā yǒu qián le.)
2. 他有钱。(tā yǒu qián.)