之后/之前/之中/之内 (formal localizers with 之)

Structure noun／clause + 之 + 后／前／中／内／间

This family of localizers links a noun or clause via the formal particle 之 (zhī) to a reference point: 之后 "after", 之前 "before", 之中 "in the midst of / among", 之内 "within (a span or limit)", 之间 "between (two points)", 之外 "outside of / besides". 之后 and 之前 alternate with the colloquial 以后/以前, but 之中、之内、之间 belong squarely to written, formal register: 言谈之中 "in the course of conversation", 两年之内 "within two years", 此事在意料之中 "this was within expectation". The 之 makes the phrase compact and bookish; everyday speech prefers 里面、当中 or 以内.

Examples

这zhè项xiàng工gōng程chéng必bì须xū在zài两liǎng年nián之zhī内nèi完wán成chéng。
This project must be completed within two years.
言yán谈tán之zhī中zhōng，他tā流liú露lù出chū几jǐ分fēn得dé意yì。
In the course of the conversation, he let a touch of smugness show.
此cǐ事shì完wán全quán在zài意yì料liào之zhī中zhōng，并bìng不bù令lìng人rén意yì外wài。
This was entirely within expectation and surprised no one.
两liǎng国guó之zhī间jiān的de分fēn歧qí并bìng非fēi一yī日rì之zhī间jiān形xíng成chéng。
The differences between the two countries did not arise overnight.

Levels are indicative: they follow the standard Chinese Grammar Wiki (AllSet Learning) progression, not an official HSK 3.0 mapping. We never assign levels by eye.

This point and the other 370, with audio on every example, inside Wanyu.