litmus

1495, earlier lytmos, from Old Norse litmosi (“moss used for dyeing”), from lita (“to dye, stain”), from litr (“colour, dye, blee”), from Proto-Germanic *wlitiz, *wlituz (“appearance, blee”), from Proto-Indo-European *wel- (“to see”) + mosi (“moss”). Cognate with Old English wlite (“appearance, form, brightness, countenance”). More at moss.

litmus (countable and uncountable, plural litmuses)

1. (uncountable) A dyestuff extracted from certain lichens, that changes color when exposed to pH levels greater than or less than certain critical levels.
2. A simple test of acidity in a liquid using litmus, usually in the form of litmus paper.
3. A simple test of any attribute; a litmus test.

• (dyestuff from lichen): lacmus

• litmus paper
• litmus test

• Roccella tinctoria
• Roccella fuciformis
• Roccella pygmaea
• Roccella phycopsis
• Lecanora tartarea
• Variolaria dealbata
• Ochrolechia parella
• Parmotrema tinctorum
• Parmelia
• Roccella montagnei
• Dendrographa leucophoea

• multis, slum it, sultim, tilmus