justify：to justify a decision, action, or idea means to show or prove that it is reasonable ,right, true or necessary.
The end justifies the means.
The new features of iPhone Xs cannot justify its hefty price tag.
The increasingly high cost of a few extra square feet of housing, not to mention of providing a good education, also makes it economically harder to justify more children.
I was earning five hundred dollars a month, which enabled me to buy a new car. I couldn’t justify another MG, so I bought a Plymouth Valiant. ”（我没理由再买一辆MG）
“Though the company was on track to double sales for a fifth straight year, it still couldn’t justify a salary for its cofounder. ”（虽然生意不错，但还不是给自己发工资的时候.）
When you run around an oval track, or down an empty road, you have no real destination. At least, none that can fully justify the effort. The act itself becomes the destination.（所谓的终点不能完美的诠释为此所付出的全部努力.）我们努力奔跑并不是为了某个固定的终点，而是拼尽全力。
The situation was grave enough to justify further investigation. 形势如此严峻，有理由做进一步的调查
Replacing the printers is difficult to justify in terms of cost.
从成本方面很难说更换打印机是合算的
翻译：
他的决定从经济上完全可以理解，但从道德上很难成立。
His decision can be entirely justified economically, but can hardly be justified morally.
（参考翻译：His decision can be justified from an economic point of view but can hardly be morally/ethically justified.）
活学活用:
Having a kid is one of the top three excuses strippers use to justify their career choice.
I don't justify myself to you.（我没必要向你解释。）
Don't help him justify his laziness/bad behavior.（别惯着他的懒惰或坏行为。）
Legitimacy are the claims which are made by those who have power ,which tried to justify why it is reasonable.
I hate to even justify the rumor with a response.（这简直是无稽之谈）.