>>40513384 (OP)Colloquially, can be. Sticking to real terms, no. Ghosts are dead people. Spirits can be any entity with a degree of consciousness that is astral or energetic.
If you want to be very strict about things when considering if calling upon some old dead person is a spirit or ghost, think of it like this. Everybody's spirit-self, your soul, resides around for a while after you die. After a while, you leave and reincarnate or go to some higher place. If someone "summons" you, you are not there anymore to summon. However, people can still call upon you anyways. This is because every spirit leaves an impression of sort into reality, a memory imprinted on the universe so to speak. People with greater impacts in life can leave a stronger residue, a stronger impression of themselves upon reality. And it is that impression, empty of the actual person, which is called upon.
Think of it in taoist lingo, yang is "you" as the self and yin is this memory-impression. At some point, yang dissipates leaving behind yin. Most fresh ghosts have yang still in them, the person, which can be helped. Only a few ghosts have left all yang behind yet still remain, certain vengeful spirits and earthbound ones. These are exceptionally dangerous and will crave yang, nothing else comes even as close to as dangerous. As of note, it is funny how similar spirit (non-person/ghost) offerings or demon offerings can offer some yang lifeforce for greater effects to feed, but that's out of this topic.