These adverbs could be placed before verbs or adjectives to signify that something is ‘about to’ or ‘will’ happen.
When indicating an impending action or event in a sentence, the use of the adverb kuài yào (快要) is preferable, to be precise, kuài yào (快要) translates to “just about to”, which conveys a sense of imminence in time. The use of sentence-final le (了) is often necessary when kuài yào (快要) is employed in a sentence. Jí jiāng (即將) is another adverb that is an indication of an impending event, but unlike kuài yào (快要), it is generally used in more formal contexts. Moreover, the adverb Jiù yào (就要) could be used to replace kuài yào (快要) as well as jí jiāng (即將) in most instances.
jiā lǐ de yán kuài yào chī wán le, wǒ zài qù mǎi yì bāo.
We're running out of salt, I will buy another pack.
yǎn chū jí jiāng kāi shǐ, qǐng dà jiā jìn kuài rù zuò.
The performance is just about to begin. Please be seated as soon as possible.
With jiù yào (就要), the event duration being indicated could be relatively short. For example, in the following sentence, although the speaker’s graduation is still two years hence, the subjective feeling being conveyed by the used of jiù yào (就要) is that two years is a quite short time. This is because jiù (就) in jiù yào (就要) implies its usage of imparting a sense of earliness. The sentence-final particle le (了) is also necessary for sentences containing jiù yào (就要).
hái yǒu liǎng nián wǒ jiù yào bì yè le, shí jiān guò de zhēn de tài kuài le.
I will graduate in just two years. Time flies so fast.
Also, the use of jiù yào (就要) could signify a more specific time. When a specific moment is mentioned in a sentence, jiù yào (就要) should be used rather than kuài yào (快要) and jí jiāng (即將).
hái yǒu liǎng gè xiǎo shí tā jiù yào huí lái le.
He will be back in two hours.
Both jiāng yào (將要) and jí jiāng (即將) could imply that something is about to happen shortly, but jiāng yào (將要) lacks the sense of imminence in time than jí jiāng (即將) has. Furthermore, the period denoted by jiāng yào (將要) could be longer, and it is an adverb that is generally used in formal contexts, much like jí jiāng (即將).
wǒ men gōng sī míng nián jiāng yào/ jí jiāng tuī chū yí xì liè xīn chǎn pǐn.
Our company is about to release a series of new products.
Suggestion of imminence
Bounded by le (了)
Denotes specific time
jiù yào (就要)
kuài yào (快要)
jí jiāng (即將)