Ratify and rectify are words paronyms (they have almost identical spelling and pronunciation, but different meanings). For this reason, they are often confused by many people.
Meaning of Ratify
Ratify means confirm, reaffirm, prove or validate something. The meaning will always be one of confirmation, approval or agreement.
Some examples of situations in which the word "ratify" applies:
Confirm: The defendant ratified his arguments.
Reaffirm: I ratify everything she said.
Prove: The facts confirmed our predictions.
Validate: The ratification of the Treaty was made through a popular referendum.
Learn more about this verb at: meaning of ratifying.
Meaning of Rectify
Rectifying has many meanings and depends on the context in which it is used. It is most commonly used in the sense of correct or amend, to go back on some statement mentioned earlier. The term is derived from "straight", that is, it has the meaning of aligning, straightening.
Some examples the application of the word "rectify":
I will rectify the company data.
It is necessary to amend the third paragraph of the contract.
In Brazil, a very popular situation is the use of "rectifying" in the sense of "reconditioning" the car engine, that is, putting it in perfect working condition. It's the work done in an "engine overhaul".
An example of a sentence: I need to repair my car engine urgently.
To learn more, read the meaning of rectify.