回
huí
回: replies and strength both 'come back'
The picture Something that went out loops around and lands back where it started. 去 leaves here and heads over there; 回 is what left coming back around to its own place.
Where the picture shows up in 回
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your body goes back
我六点回家。
wǒ liù diǎn huí jiā
I get home at six.
The feet that left in the morning step back onto that same doorstep in the evening.
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words go back to the sender
他还没回我信息。
tā hái méi huí wǒ xìnxī
He still hasn't replied to me.
The message you sent reaches the other side and comes back to your screen as a reply.
回信息 pictures the message you sent making its way back to you.
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your head turns back
你回头看看。
nǐ huí tóu kàn kan
Turn around and take a look.
A face that was looking ahead swings back over the shoulder.
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strength comes back into the body
病人的力气慢慢回来了。
bìngrén de lìqi mànmàn huí lái le
The patient's strength is slowly coming back.
The color that drained away creeps back into the patient's face.
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the talk comes back on track
话说回来，他也不容易。
huà shuō huí lái, tā yě bù róngyì
That said, it hasn't been easy for him either.
You reach out, pull the wandering conversation back, and set it down on its first line again.
话说回来 pulls a conversation that drifted back to where it started.
All of it in one picture
回 is something going out, looping round, and landing back where it started. The feet that left in the morning come back to that doorstep; the message you sent comes back to your screen as a reply. The head turns back over the shoulder, the strength comes back into the body, and the conversation that wandered off comes back to its first line. So every 回 traces the same curve: out, around, and home to its own place.