Almost ring
An almost ring is like a toy box with some toys missing. Normally, a toy box would have all kinds of toys, but in an almost ring, there might be some toys missing.
In the same way, a ring normally has things called "multiplicative inverses" for every number, which is a fancy way of saying that each number in the ring has a buddy that they can multiply with to get a special number called "1". But in an almost ring, some of the numbers might not have a buddy to multiply with to get 1, just like some of the toys might be missing from the toy box.
It's still a type of ring, but it's a bit different because not all the numbers have buddies for multiplication. Sometimes, mathematicians study almost rings because they can still be useful even if they're not "perfect" like regular rings.
In the same way, a ring normally has things called "multiplicative inverses" for every number, which is a fancy way of saying that each number in the ring has a buddy that they can multiply with to get a special number called "1". But in an almost ring, some of the numbers might not have a buddy to multiply with to get 1, just like some of the toys might be missing from the toy box.
It's still a type of ring, but it's a bit different because not all the numbers have buddies for multiplication. Sometimes, mathematicians study almost rings because they can still be useful even if they're not "perfect" like regular rings.