73:8

And remember the name of your Lord and devote yourself to Him with [complete] devotion.
Meaning:-
Devote: to apply or dedicate (oneself, time, etc) to some pursuit.
devotion: loyalty, faithfulness, dedication; commitment.

73:14

On the Day when the earth and the mountains will be in violent shake, and the mountains will be a heap of sand poured out and flowing down.
Meaning:-
Heap: a great number or large quantity.

73:17

If you persist in unbelief, how will you save yourselves on that Day which shall turn the children grey-headed (old),
Meaning:-
Persist: continue firmly, carry on, keep on, remain.

73:20

Indeed, your Lord knows, [O Muhammad], that you stand [in prayer] almost two thirds of the night or half of it or a third of it, and [so do] a group of those with you. And Allah determines [the extent of] the night and the day. He has known that you [Muslims] will not be able to do it and has turned to you in forgiveness, so recite what is easy [for you] of the Qur’an. He has known that there will be among you those who are ill and others traveling throughout the land seeking [something] of the bounty of Allah and others fighting for the cause of Allah . So recite what is easy from it and establish prayer and give zakah and give to Allah a goodly loan. And whatever good you put forward for yourselves – you will find it with Allah . It is better and greater in reward. And seek forgiveness of Allah . Indeed, Allah is Forgiving and Merciful.
Meaning:-
Bounty: generosity; liberality, a monetary gift or reward.