Learn English – the difference between the prefix iso and homo

Note - In systems:

Validate (to check the aliveness, legal status, existence of data). To check the ‘validity’ of data - does it comply with the ‘legal’ or required format of the system.

Verify (to check the truth) - to check whether something is true. To verify that a user exists, verify that an account is current, to ‘check the truth of’ ... anything.

Validation - Validate: means ‘having force in law, legally binding’, from the Latin - validus -"strong, effective, powerful, active". Validation is ‘the process of checking that something is legally or currently active.’

Examples:

• ‘Sorry sir. Your passport is no longer valid. It’s out of date’.
• ‘Sorry, your gift voucher is no longer valid, it expired’.

• ‘Sorry madam - our validation has shown that this cheque isn’t real - it’s a fake’.

• When our system tries to validate this email address we see it is invalid, it uses the wrong format

• This email address is invalid - the user doesn’t exist

https://www.etymonline.com/word/valid

Verification - Verify - is from the Latin ‘verus’ or truth. It means ‘to check the truth’ or - check if (something is) true. Verification is ‘the process of checking whether something is true’.

Examples:

• We have verified the image on your passport and confirm that it is your true image.
• We have checked your blood and can verify (note - it means ‘state as true’) that you do not have anaemia.
• Our verification of your order is complete and we can confirm that the box we sent you contains 15 white hats and 5 green.
• We cannot verify this email user on our server. They don’t seem to exist.

https://www.etymonline.com/word/verify

Surely there should be more of a difference between the two words. If they mean the same thing surely there would be no need anymore for two words

There are a lot of near synonyms in English, so this does not follow at all. It's particularly so when you consider that act entered the English language in the late Middle English period, from French, while deed was in the language from the very beginnings of Old English. Many, but not all, seeming redundancies in English vocabulary have a similar origin story.

It is true that there are differences in nuances. The primary one would be that an act would generally be need to be relatively remarkable before we would use the term deed. One can do a particularly brave or noble or dastardly or evil deed, but one can't really do a lazy or everyday or common deed. There's nothing technically wrong with the latter, but it wouldn't be an idiomatic use.

There are similarly some differences in what verbs and prepositions are used with either. One doesn't do an act, one cannot be in the deed of anything.