Something is swollen if it is larger than it should be. Body parts that are swollen are usually filled with fluid, and can be very painful. The man in the picture has a swollen ankle.
A sword is a weapon that was used by knights many hundreds of years ago. Swords are usually around 2-3 feet long, made of steel, and have a straight or slightly curved blade that is sharp on both edges. The part of the sword you hold is called the hilt. Most swords have a casing that they could be stored in so the owner wouldn't hurt themselves, this is called a scabbard or a sheath.
A symbol is a kind of picture that means something. Symbols are often used on signs, where they can express a lot of information that you can understand quicker and easier than writing.
Something is symmetric if it exhibits symmetry, that is if you draw a line down the middle of it, the two sides are mirror images of each other.
Symmetry means that if you draw a line through something, usually down the middle, then the two halves of it are identical but reversed - like looking into a mirror. Things that are symmetrical are usually nice to look at. People's faces are symmetrical because if you draw a line down the middle of your face the left and right sides are the same. In fact, your entire body is symmetrical, as are animal's faces and bodies. Lots of everyday things are symmetrical. How many symmetrical things can you see around you? The picture is a shape that is symmetrical along the left and right half and the top and bottom halves. The opposite of symmetry is asymmetry.
You synchronize two or more actions when you do them at exactly the same time. The two men in the photo are practicing synchronized diving. People will also synchronize their watches to make sure they will all get to the same event at the same time.
A syringe is a device that is used for putting a measured quantity of fluid into something else. Syringes are often, but not always, fitted with a sharp, hollow point at one end for injecting liquids into things. Syringes can be used for things as diverse as feeding baby animals, or for injecting medicine into you.
Syrup is a thick, sweet liquid. Syrup can be made from dissolving sugar in water or it might be made from a naturally sweet liquid, like maple syrup.