Yìzhí 一直 is a time adverb used to show continuity in actions or states from a point in the past up to the point being talked about or into the future. It is important to note that yìzhí 一直 means ‘continuously’ or ‘consistently’ over time, not ‘every day’ or ‘usually.’ Depending on context yìzhí 一直 can translate into ‘continuously’, ‘always’ or ‘all along’.

Structure
Basic form
Yìzhí 一直 ‘continuously’ is placed after the subject and before the main verb or adjective in a sentence.
To emphasise the continuity of an action, yìzhí 一直 ‘continuously’ is often followed by the progressive aspect marker zài 在.
Also check: The progressive aspect marker zài 在
A modal verb can be placed before or after yìzhí 一直 ‘continuously’ dependent on context. When emphasising the ability or intention to continue an action or a state into the future, yìzhí 一直 comes after the modal verb.
When emphasising a consistent ability, desire or state, yìzhí 一直 ‘continuously’ comes before the modal verb.
Negation
The negation adverb is placed after yìzhí一直 ‘continuously’.
The negation adverb méi 没/沒 is frequently used to indicate that an expected action or event has not occurred up to now or during a period of time in the past.
The negation adverb bù 不 can be used instead of méi 没/沒. However, bù 不 sometimes carries a tone of persistent refusal or unchanged attitude. It is mainly used in colloquial or narrative contexts.
If the predicate is an adjective, only bù 不 can be used.
Question
The most common way to form a yes-no question is to add the question particle ma 吗/嗎 at the end of the sentence.
With adverbs
The adverb dōu 都 ‘all; both’ is often placed after yìzhī 一直 ‘continuously’ to add emphasis to the continuous nature of something.
With prepositional phrases
Yìzhī 一直 ‘continuously’ is usually placed before the prepositional phrase. In this pattern, yìzhī 一直 modifies the entire action, including the location or direction provided by the prepositional phrase.
If the prepositional phrase is placed before yìzhī 一直 ‘continuously’, it sets the scene first and then uses yìzhī 一直 to describe what happened continuously within that scene. Here yìzhī 一直 emphasizes the state or action within that specific context.
Functions
1. Yìzhī 一直 expressing ‘continuous action over time’
Yìzhí 一直 indicates that an action or situation has continued without stopping from a time in the past up to now or up to a reference point. It modifies the verb or adjective to express that the action keeps going without stopping.
The progressive aspect marker zài 在 is generally used with verbs that describe ongoing activities, especially in the present or recent past.
2. Yìzhī 一直 expressing consistent state, habit, or attitude
Yìzhí 一直 indicates that someone has done the same thing repeatedly or has held the same opinion or emotional state for a long time.
Yìzhí 一直 is often used with bù 不 for consistent refusal, disagreement, etc. Yìzhí bù 一直不 is often translated into ‘never’.
3. Yìzhī 一直 expressing a long-standing desire or feeling
With verbs like xiǎng 想 ‘want’, xǐhuan 喜欢/喜歡 ‘like’, xīwàng 希望 ‘hope’, or adjectives, yìzhí 一直 indicates emotional or mental states that have lasted over time.
Note, you do not use the progressive aspect marker zài 在 here, because it is not about an ongoing action, but about a mental or emotional state that has lasted over time.
4. Yìzhī 一直 expressing spatial continuity or direction
Used with motion verbs yìzhí 一直 means to go straight ahead or keep going in one direction without turning. It is often used to give directions.