Verb Tenses in Chinese
Western languages such as English have several ways to express tense. The most common are verb conjunctions which change the form of the verb depending on the time frame. For example, the English verb "eat" can be changed to "ate" for past actions and "eating" for current actions.
Mandarin Chinese does not have any verb conjugations. All verbs have a single form. For example, the verb for "eat" is 吃 (chī), which can be used for the past, present, and future.
Despite the lack of Mandarin verb conjugations, there are other ways to express timeframes in Mandarin Chinese.
STATE THE DATE
The simplest way to clarify which tense you are speaking in is to directly state the time expression (like today, tomorrow, yesterday) as part of the sentence. In Chinese, this is usually at the beginning of the sentence. For example:
Zuótiān wǒ chī zhū ròu.
Yesterday I ate pork.
Once the timeframe is established, it is understood and can be omitted from the rest of the conversation.
The particle 了 (le) is used to indicate that an action occurred in the past and has been completed. Like the time expression, it can be omitted once the timeframe has been established:
(Zuótiān) wǒ chī zhū ròu le.
(Yesterday) I ate pork.
The particle 了 (le) can also be used for the immediate future, so be careful of its usage and be sure to understand both functions.
When you have done something in the past, this action can be described with the verb-suffix 過 / 过 (guò). For example, if you want to say that you have already seen the movie "Crouching Tiger, Hidden Dragon" (臥虎藏龍/卧虎藏龙 - wò hǔ cáng long), you can say:
Wǒ yǐjīng kàn guò wò hǔ cáng long.
Unlike the particle 了 (le), the verb suffix guò (過 / 过) is used to talk about an unspecific past. If you want to say that you saw the movie "Crouching Tiger, Hidden Dragon" yesterday, you would say:
Zuótiān wǒ kàn wò hǔ cáng lóng le.
COMPLETED ACTIONS IN THE FUTURE
As mentioned above, the particle 了 (le) can be used for the future as well as the past. When used with a time expression such as 明天 (míngtīan - tomorrow), the meaning is similar to the English perfective. Take for instance:
Míngtiān wǒ jiù huì qù Táiběi le.
Tomorrow I will have gone to Taipei.
The near future is expressed with the combination of the particles 要 (yào - to intend); 就 (jiù - right away); or 快 (kuài - soon) with the particle 了 (le):
Wǒ yào qù Táiběi le.
I'm just going to Taipei.
When an action is continuing to the present moment, the expressions 正在 (zhèngzài), 正 (zhèng) or 在 (zài) can be used, along with the particle 呢 (ne) at the end of the sentence. This can look something like:
Wǒ zhèngzài chīfàn ne.
I am eating.
Wǒ zhèng chīfàn ne.
I am eating.
Wǒ zài chīfàn ne.
I am eating.
Wǒ chīfàn ne.
I am eating.
The continuative action phrase is negated with 没 (méi), and 正在 (zhèngzài) is omitted.
The 呢 (ne), however, remains. For example:
Wǒ méi chīfàn ne.
I am not eating.
MANDARIN CHINESE TENSES
It is often said that Mandarin Chinese does not have any tenses. If "tenses" mean verb conjugation, this is true, since verbs in Chinese have an unchangeable form. However, as we can see in the above examples, there are many ways to express timeframes in Mandarin Chinese.
The main difference in terms of grammar between Mandarin Chinese and European languages is that once a timeframe has been established in Mandarin Chinese, there is no longer any need for precision. This means sentences are constructed in simple forms without verb endings or other qualifiers.
When talking to a native Mandarin Chinese speaker, Westerners may get confused with this lack of continuous precision. But this confusion arises from the comparison between English (and other Western languages) and Mandarin Chinese.
Western languages require subject/verb agreements, without which the language will be glaringly wrong. Compare this with Mandarin Chinese, in which a simple statement can be in any timeframe, or express a question, or be an answer.