jiàoliàn zhèngzài jiāo zhège dòngzuò.

正在 marks an action that is in progress right now. In this sentence, it shows that the coach is currently teaching the move.

So:

• 教练教这个动作。 = The coach teaches / is teaching this move.
• 教练正在教这个动作。 = The coach is teaching this move right now.

It is similar to the English idea of be doing.

Yes. 在 and 正在 can both mark an ongoing action.

• 教练在教这个动作。
• 教练正在教这个动作。

Both are natural. The difference is mainly one of emphasis:

• 在 = more neutral
• 正在 = a bit more explicit or emphatic about right now / in the middle of

You may also hear:

• 教练正在教这个动作呢。

The 呢 can make the ongoing sense sound even more immediate or conversational.

Because 教 has more than one pronunciation and meaning.

Here it is jiāo, meaning to teach.

Common pronunciations:

• jiāo = to teach
  
  • 教学生 = teach students
• jiào = religion / to make someone do something in some older or formal uses, or in words like 睡觉 where the character is different in modern analysis

In this sentence, 教练正在教这个动作, the second 教 clearly means teach, so it is jiāo.

This is a very common point of confusion because 教练 starts with jiào, but the verb 教 is jiāo.

• 教练 = jiàoliàn
• 教 = jiāo

Yes, literally it is:

• 这 = this
• 个 = measure word
• 动作 = movement / action / move

So 这个动作 literally means this movement/action.

In natural English, depending on context, it could be translated as:

• this move
• this motion
• this technique
• this action

In sports, dance, martial arts, or fitness, this move is often the most natural translation.

In Mandarin, when a demonstrative like 这 or 那 is used before a noun, you usually need a measure word in between.

The pattern is:

• 这/那 + measure word + noun

So:

• 这个动作 = this move
• 那个老师 = that teacher
• 这个学生 = this student

Here, 个 is the measure word. It is the most common general measure word.

For 动作, 个 is completely normal in everyday speech.

动作 often refers to a physical movement, motion, or move.

In different contexts, it can mean:

• a dance move
• a martial arts move
• an exercise movement
• a sports technique
• a physical action

In this sentence, since a coach is teaching it, 动作 most likely means a move or technique rather than a broad abstract action.

So in context, this move is probably the best English sense.

Because Mandarin does not need a verb like is in this kind of sentence.

English says:

• The coach is teaching this move.

But in Mandarin, the ongoing marker 正在 already helps express that idea:

• 教练正在教这个动作。

Also, 是 is not used before ordinary action verbs like 教.

Incorrect:

• 教练是正在教这个动作。

Correct:

• 教练正在教这个动作。

So if the main verb is an action like teach, eat, run, study, you usually do not add 是.

Yes, it is quite similar here.

The structure is:

• 教练 = subject
• 正在 = ongoing-action marker
• 教 = verb
• 这个动作 = object

So the pattern is:

Subject + ongoing marker + verb + object

That is close to English:

The coach + is + teaching + this move

This is one reason why this sentence is relatively straightforward for English speakers.

Yes. If you remove 正在, the sentence is still grammatical:

• 教练教这个动作。

But the meaning becomes less specifically focused on the action being in progress at this exact moment. It could mean:

• the coach teaches this move
• the coach is teaching this move
• the coach teaches this kind of move

So 正在 helps narrow it to right now, in the middle of doing it.

Not exactly. 教 means to teach, not simply to demonstrate.

So 教练正在教这个动作 means the coach is teaching the move. That may include demonstrating it, explaining it, correcting it, or guiding someone through it.

If you specifically want to say demonstrating, you would more likely use a verb such as:

• 示范 = demonstrate

For example:

• 教练正在示范这个动作。
  = The coach is demonstrating this move.

So:

• 教 = teach
• 示范 = demonstrate

They are related, but not identical.

The sentence does not specify the learner. Mandarin often leaves out information that is understood from context.

So 教练正在教这个动作。 simply means:

• The coach is teaching this move.

If you want to say who is learning it, you can add that person:

• 教练正在教学生这个动作。
  = The coach is teaching the students this move.

• 教练正在教我这个动作。
  = The coach is teaching me this move.

In other words, the sentence is complete without stating the learner, just like English can say The coach is teaching this move.

Mostly, 教练 means coach or trainer, especially in sports, fitness, dance, driving, and similar skill-based training.

Examples:

• 足球教练 = soccer coach
• 健身教练 = fitness trainer
• 驾校教练 = driving instructor

So in this sentence, 教练 strongly suggests someone training others in a practical skill or physical technique.

Sometimes, but they are not exactly the same.

• 动作 = movement / move / action
• 姿势 = posture / pose

Use 动作 when you mean the actual movement or technique. Use 姿势 when you mean the body position or pose.

For example:

• 教练正在教这个动作。
  = The coach is teaching this move.

• 教练正在纠正这个姿势。
  = The coach is correcting this posture.

If the thing being taught is dynamic, 动作 is usually better.

It is understandable, but it is usually more natural to put the person directly after 教:

• 教练正在教我这个动作。

This pattern is very common:

• 教 + person + thing

Examples:

• 老师教我中文。 = The teacher teaches me Chinese.
• 教练教他这个动作。 = The coach teaches him this move.

Using 给 after 教 is usually unnecessary here.

Mandarin nouns usually do not change form for singular or plural the way English nouns do.

So 教练 can mean:

• coach
• coaches

The context tells you which one is meant.

In this sentence, most people would naturally understand it as singular:

• The coach is teaching this move.

If you want to make it clearly plural, you could say something like:

• 几个教练正在教这个动作。
  = Several coaches are teaching this move.

It is natural and standard Mandarin.

It works well in many real situations, especially when talking about sports, exercise, dance, martial arts, or training.

A few natural variations are:

• 教练在教这个动作。
• 教练正在教这个动作呢。
• 教练在教我们这个动作。

So the original sentence is a good, normal model sentence.