What does "due" mean as in "due diligence" or "due procedure"?

That meaning applies in "due diligence" and "due process", but "due procedure" doesn't really mean anything. It would either be "due process" or "proper procedure".

You can read it as (the required) diligence or (the required) procedure. Required, expected, appropriate. You debt was due: The time you were expected to pay it back had come. The bus was due at 9pm: The bus was expected at 9pm. Due diligence: act with the expected amount of diligence. That sort of meaning.

“Due” typically means the amount that is owed or required. Think a phone bill. You have $60 due at the end of the month. You have to pay $60. So due diligence should be read as “the amount of diligence that is required for the task”. Same for due procedure.

The same definition applies. Similarly, saying, “With all due respect, this is not the report I asked for,” means, “I don’t intend to disrespect you; I want to give you all the respect you deserve. But I have to say, this is not the report I asked you for.” Doing your due diligence is acting as diligently as you should. “Due process” is a set phrase which refers to the process that a suspect/[defendant](https://www.dictionary.com/browse/defendant%23american-defendant) is entitled to (is due) or subject to, in accordance with the law. Even criminals are granted certain rights under the law. It’s grammatical to say that these rights are due to them, and even criminals are due certain rights.

I think you probably meant “due process,” which is a standard term in law (it appears in the U.S. Constitution). It means the amount of process that is required/appropriate. (Process in this case meaning legal process — that is, hearings, the opportunity to make an argument to the court, etc.)

Due here means “what is expected or deserved” so the diligence that is deserved to be taken, or the procedure that is expected to be followed.

Close to "proper" ... "due time" -- the proper amount of time to do something "due process" -- the proper procedures as per custom and law "due diligence" -- the proper work to investigate something with care, focus, and attention "Proper" here can mean what is customary, required, imposed, necessary, expected, owed.

Not the same. Due diligence means being careful; adhering to standards. Doing what is expected. Taking any reasonable steps. Due procedure means following the instructions. Not deviating from the standard methods. Obeying the rules. Going by the book. For a policeman investigating a crime (for example), Due dilligence would be interviewing all witnesses. Due procedure would be recording all of those interviews.

Oh, good question! 😊 I actually wondered about this too when I first heard "due diligence." From what I understand, in phrases like that, "due" means something like "proper" or "appropriate" like doing the right amount of research (due diligence) or following the correct steps (due procedure). Btw, I’ve been picking up little things like this from a small Discord server called **VozMate** it’s pretty new but they share daily English tips and have voice channels for practice. 

Another usage of this word, and one in American news a lot at the moment, is "due process". "Due" in this usage has a formal or legal implication. It means "A thorough or defined method by which the thing is done". It means that the activity is to be taken seriously and that either there is a set protocol, or that there is no specific protocol but that you should take extra effort to double-check your work and make sure it was done right. "Due diligence" - 'diligence' conveys the sense of being on guard. It suggests an extra layer of checking or monitoring, that extra attention is being given. "Due procedure" - there is probably a protocol to follow, or a maybe someone has a checklist you should consult before you declare you are done with a project so you can make sure you didn't miss something. "Due process" - this refers to a set of legal obligations a government has to meet, the government can't simply accuse you of something and be done with it. You have the right to challenge the accusation, you have the right to legal counsel (a lawyer), you have the right to refuse to answer questions from an interrogator, you have the right to learn what evidence or assertion is being used to justify the accusation, you have the right to appeal a decision, and so on. If the government convicts you while denying you these rights then you can take the government to court instead, and sometimes people do succeed in doing that! This one is in the news right now because the Trump administration officials believe they can deport immigrants without providing them a court hearing or the opportunity to prove that they have documents or status, and that an accusation is enough; this assertion is currently making its way through the court system in some high profile situations wherein the immigration agents missed or ignored papers that someone has or had, and due to that mistake the person was wrongly deported. The contention from the Trump administration is that once someone is deported, it can not be reversed even if the facts later prove the agent to have been in error; the deported people (or rather, lawyers and organizations challenging the government) assert that by ignoring due process (hearings, opportunities for a defendant to present favorable evidence, etc) that the government has and will continue to deport people who are not eligible for deportation. *edit: and the administration asserts that non-citizens are not owed a hearing, that this is a right reserved only for citizens* I don't want to get into whether the government approach is right or wrong here, that is a discussion for a different sub-reddit, but it is an easy example of what "Due Process" is and one you will hear about in the news for the next few months or years.

Think of “due” as either required/necessary or the point at which something is required.

"Of proper quality or extent" is the correct definition for "due" in both "due process" and "due diligence." "Due process" means that people being accused of a crime are entitled to a proper process before their rights, freedom, or property is taken away. The state cannot just take something from its citizens whenever and however it wants; it must follow the proper procedure. "Due diligence" means that a matter should receive a proper amount of attention and investigation before committing to something. This is often used in business and means that a topic should be researched before committing resources to it.

It’s the same meaning.