In personal meaning, "precisa" is polite. "Preciso de sua ajuda!". If you use "exige" in the same sentence, you are obligating someone to help you: "Exigo sua ajuda!". It is not a good idea! For things or qualifications for a job, "exigir" is like "to require". If you would like to try some examples, I could help you.

Hello Michael! Both words can be used for "people" and for "things" contexts. In some cases, they have similar meaning but they are not interchangeable. I hope this information bellow can be useful. Meaning - EXIGIR: to claim, to demand, to require, to urge, to impose (as obligation or a duty); - PRECISAR: to need, must , have to, need to; Keeping the meaning in mind, we can see some examples: 1) - Michael precisa de uma resposta para esta pergunta. (Michael needs an answer for this question) - Michael exige uma resposta para esta pergunta. (Michael requires an nswer for this question) 2) - Esta pergunta precisa ser respondida. (This question needs to be answered) - Esta pergunta exige uma resposta. (This question requires an answer) 3) - Eu preciso do Michael para saber se esta explicação foi clara. (I need Michael to know if I this answer was clear) - Eu exijo que o Michael diga se esta explicação foi clara. (I impose to Michael that he tells me if this answer was clear) In these examples above, EXIGIR and PRECISAR can be used in similar situations both for people and for things. But they have diferent meanings. ------- P.S.: - Sorry my bad English - I hope I could get the idea when you say "for things" and "for people". If not, please let me know if you need more information.

In this case, there is a direct translation to english: 'exigir' means to demand while 'precisar' means to need. Eu exijo sua presença: I demand your presence Eu preciso da sua presença: I need your presence As simples as it is. As for '+ de': With the verb 'precisar' you must always use 'de' except when you have a verb after: ex: Eu preciso de comida = I need food Eu preciso comer = I need to eat comer is a verb, therefore you should not use 'de' while comida is not a verb, so you use 'de'.

Michael, I agree with the previous responses and I would like to add some examples that I found in Brazilian songs: 1)”Exijo respeito, não sou mais um sonhador.” “I demand respect. I'm no longer a dreamer.” (song: “Samba do grande amor” - Chico Buarque) http://lyricstranslate.com/pt-br/samba-do-grande-amor-samba-great-love.html 2)”Eu acho, meu amor, e só se pode achar que a luz dos olhos meus precisa se casar.” “I think, my love, and that's the only thing to think: that the light in my eyes needs to get married.” (Pela luz dos olhos teus – Vinícius de Moraes) http://lyricstranslate.com/pt-br/pela-luz-dos-olhos-teus-light-your-eyes.html 3)”Deixe-me ir, preciso andar.” “Let me go, I need to walk” (Song: “Preciso me encontrar” - Cartola) http://lyricstranslate.com/en/preciso-me-encontrar-i-need-find-myself.html 4)”O ambiente exige respeito.” “The environment demands respect.” (Song: “Estatuto da gafieira” - Billy Blanco) https://www.letras.mus.br/billy-blanco/376613/