Can I legally seize somebody's property?

If I found an item in a store I really want but can't pay for it, can I just seize it?

Or if somebody left their iPhone right by themselves and I seized it without any physical bodily harm to the individual, that is completely legal, right? Or is it considered theft?

I honestly don't get it. Under most civil forfeiture laws, seizure is not considered theft.

HOWEVER, if seizure IS considered theft, then whoever seizes your personal property can legally be charged for a crime then, correct?

Instead of demanding the seized property back from a law enforcement agency, can't you just press charges against the officer who stole your property?

You can't have it either way. Seizure is either theft and you can press charges against anyone who stole your property; or seizure is completely different than theft thus makes it legal to seize anything from anybody or anything.

I request answers from somebody who has at least studied law before, and not some dimwit who has an opinionated response.

Thanks!

Added (1). https://www.vocabulary.com/dictionary/seizure&sa=U&ved=0ahUKEwiy-OisuNTjAhVxKH0KHWmQC6MQFggPMAE&usg=AOvVaw05eJlp-xuiUPO40EaZTLX5

No where in that definition does it state that seizure only pertains to governmental or law enforcement agencies.

As a civilian, if I publicly say I seized property on suspicion of it being used for criminal activity, it is completely legal to do so.

No due process needed.

Added (2). If seizure is theft, why don't people (who had this happen to them) take the law enforcement officer whomever stole their property and PRESS CHARGES against the individual and convict them of a felony if the amount of value was above the certain amount (which usually is because vehicles, houses, and thousands of dollars are typically confiscated) which qualifies as a felony in your state?

I'm genuinely confused

Added (3). And even if it only involves law enforcement or the government, you have to define that also.

Definition of Law Enforcement
"Law enforcement is any system by which some members of society act in an organized manner to enforce the law by discovering, deterring, rehabilitating, or punishing people who violate the rules and norms governing that society."

Added (4). Definition of Government:
gov·ern·ment/ˈɡəvər(n)mənt/
noun
the governing body of a nation, state, or community.
the relation between a governed and a governing word.

So if you worked as a librarian or post officer worker, you also have the legal state right to confiscate any private property or assets if you suspect it being involved in a crime.

You can use it to get rich just like police departments do.

Good question thanks for asking

If you will take the time to learn the "legal definition" of seize or seizure, your question will be answered. If you can't seem to manage that, what you described it outright theft. Seizure of property is something entirely different.

You can't. If you do it, then it is theft, and is completely illegal. If the government does it, then it is not considered theft and the officer can't be charged. Seizure is theft some of time and it is not theft other times. It is both ways.

That is not seizing it.
You have no warrant or court order.
You are stealing it.

You take anything that is not yours and you are committing theft.

Is "seize" the politically correct term for "theft?"