透

transparent; permeate; filter; penetrate

10 strokes. Jōyō kanji, taught in secondary school. Newspaper frequency rank 1035.

Readings

トウ (on reading): 透明 (とうめい) transparent; 透過 (とうか) penetration
すける (kun reading): 透ける (すける) to be transparent; 透け感 (すけかん) see-through sensation (for clothing)
すかす (kun reading): 透かし (すかし) watermark (in a stamp, banknote, etc.); 透かす (すかす) to look through
すく (kun reading): 透き通る (すきとおる) to be transparent; 見え透く (みえすく) to be transparent
とうる (kun reading)
とうす (kun reading)

透明 (とうめい) transparent
透過 (とうか) penetration
浸透 (しんとう) permeation (of thought, ideology, culture, etc.)
不透明 (ふとうめい) opaque
透明度 (とうめいど) transparency
透ける (すける) to be transparent
透け感 (すけかん) see-through sensation (for clothing)
明け透け (あけすけ) open
透けて写る (すけてうつる) to be seen through
濡れ透け (ぬれすけ) see-through because of wetness (e.g. clothes)
透かし (すかし) watermark (in a stamp, banknote, etc.)
透かす (すかす) to look through
肩透かし (かたすかし) under-shoulder swing-down
見透かす (みすかす) to see through (a lie, scheme, etc.)
透かし彫り (すかしぼり) sukashibori
透き通る (すきとおる) to be transparent
見え透く (みえすく) to be transparent
透く (すく) to be transparent
透き通す (すきとおす) to be visible through
透渡殿 (すきわたどの) roofed path (lacking walls) connecting the main residence and the side houses (in traditional palatial architecture)
透り (とおり) penetration (as of light)
透破 (とっぱ) ninja

116 words in all.