1 old variant of 深[shēn]

1 to understand

2 to realize

3 to find out

1 tell-tale

2 informer (esp. to police)

3 whistleblower

4 grass

1 secret code

2 ciphertext

3 password

4 PIN

1 profound

2 deep

3 deep-going

1 lit. to know one and understand half (idiom); a smattering of knowledge

2 dilettante

3 amateur

1 lit. not requiring a detailed understanding (idiom); only looking for an overview

2 not bothered with the details

3 superficial

4 content with shallow understanding

1 to talk intimately while being comparative strangers (idiom)

1 untold pain and suffering (idiom); deeply scarred for life

1 If you work at it hard enough, you can grind an iron bar into a needle.

2 cf idiom 磨杵成針|磨杵成针, to grind an iron bar down to a fine needle (idiom); fig. to persevere in a difficult task

3 to study diligently