If you ask most people to define "euthanasia", they will pause a little, then say it has something to do with helping someone who is old, or sick, or suffering, to die. They rarely consider the various complicated scenarios that crop up.
Here is a terse set of distinctions sent by a physician friend with whom a few of us were having a debate surrounding Canada's recent law legalizing euthanasia.
Before reading, I think it is useful to keep in mind that euthanasia is not about "letting" someone die of natural causes, keeping them as pain-free and comfortable as possible along the way, with nursing, food, water, etc., as distinct from keeping them alive artificially.
Rather, euthanasia is always about "making" someone die by the administration of life-ending drugs, injections, etc.
Note: MAiD = Medical Aid in Dying
Euthanasia = making someone die (with the intent to end suffering, or for some other cause deemed compassionate by those who have legalized the killing procedure and those who administer it).