lit·mus 
(lĭtməs)
(lĭtməs)n.
A water-soluble bluish powder derived from certain lichens that changes to red with increasing acidity and to deeper blue with increasing basicity.
[Middle English litemose (of Scandinavian origin; akin to Old Norse litmosi, dyer's herbs litr, color, dye + mosi, bog, moss) and Middle English lykemose (from Middle Dutch lijkmoes, variant of lēcmoes : lēken, to drip + moes, moss).]
- be off (one's) feed
- be off one's feed
- be of one mind
- be of service
- be of two minds
- be on game
- be on high horse
- be on (one's) game
- be on one's game
- be on one's high horse
- be on to
- be out of here
- Beowulf
- be prepared
- bequeath
- bequeathal
- bequeather
- bequeathment
- bequest
- Berar
- berate
- Berber
- berberine
- berceuse
- Berchtesgaden