same, together

同 is composed of the variant of 凡 and 口(mouth), 凡 is the picture of a tray or a bucket, 口 is added to represent there is a hole on the bottom, the original meaning of 同 is a bamboo tube, but such meaning has been replaced by 筒, every bamboo tube looks the same. On the other hand, both 同 and 凡 come from the same origin, now those two Hanzi have similar shapes, pronunciations and meanings.