it's probably a hyacinth. if it's in some water.
or a lily.

Yeah, looks like an amaryllis before the flower

I can't see the part in the jar very well, but if it's a round bulb, I agree it's likely an Amaryllis that is not in bloom.

The foliage also looks a bit like Agapanthus, but the bulbs on those tend to be shaped more like fingerling potatoes than round.

Amaryllis. But without its giant bloom.

I think this is a amaryllis, before it blooms?

Looks like Amaryllis to me too; beautiful when it blooms.

Or an amaryllis the next year after it blooms. Mine always get lush spiky leaves and no flower the next year.

It is a bulb with out it's bloom.
It looks like tulip leaves, without the bloom.

For kdear:

You have to betray their trust to get them to rebloom each year.

Place them in the basement or a closet with no light or water for two months and then bring them back out.

Or, place the bulbs in your crisper for two months away from apples and onions.

yep, it's a bulb, and I also think it's Amaryllis.

Can you grow amaryllis like this, just in water with no soil?

It could be a pregnant onion Ornithogalum longibracteatum - no blooms for us, but it creates lots of little starts. We have one and it just keeps on growing. On the web, there are lots of blooming ones! Ours is planted in soil, but kept very wet - the dish below rather than the soil itself.