I have a question for why these following instructions are illegal.

I have a question for why these following instructions are illegal. If you can please explain it to me because I kind of don't understand. I know it has to do with the size of bytes but I'm still a little confused by it.

Byte1 BYTE 0FFh, 1, 2

Byte2 BYTE 14h

Word1 WORD 0FFFFh, 1, 2

Word2 WORD 3

Word3 SWORD 7FFFh, 8000h

Word4 SWORD 9000h

Dword1 DWORD 10h, 20h, 30h, 40h

mov word1, byte2

mov word2, 10000h