etre vs avoir

Question

I can't seem to differentiate between the cojugate form of etre and avoir when used with the first person Je. Par exemple:
Je suis grand.
versus
J'ai cinq ans.

They both seem to mean "I am" in the above sentence.

Accepted Answer

Bonjour,
I hope that Ann's and Maarten's answers have helped make things clearer.
Here are few more links about 'être' and 'avoir':
avoir-nombre-ans-to-be-number-years-old
idioms-with-avoir
idioms-with-etre
Bonne lecture et bonne journée! ;-)

Answer

You must not 'translate literally':  the french way of telling your age is something like:  'I have 5 years'  (j'ai ...)  but in English you say 'I am'.  (sounds strange for the french:  how can you 'be' 5 years???). Same thing with other expressions:  'j'ai faim' is translated as 'I am hungry', but if you translate literally it is more like  'I have hunger'.  Same for 'j'ai soif' etc.

Answer

https://www.lawlessfrench.com/grammar/etre-lesson/

https://www.lawlessfrench.com/grammar/avoir-lesson/

https://www.lawlessfrench.com/grammar/faire-lesson/

To support what Anne says, particularly about being wary of literal translations, take a look at some of this information on être/avoir. I have included the link to 'faire' as well because it is used in specific circumstances also as the equivalent of English 'to be'. Over time, you will learn the different uses of these verbs between English and French. In many cases, it will just sound strange to the French if you use the wrong verb, but there are times you will get a raised eyebrow or a chuckle by using the wrong verb because the meaning is significantly different. You might like to search for instance on the difference in meaning between "Je suis chaud(e)/froid(e)' and "J'ai chaud(e)/froid(e)", or between "Je suis fini" and "J'ai fini".