Able to pass through or into a given semipermeable membrane or polymer(adjective)
A substance which is able to pass through or into a membrane or polymer(noun)
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Use "permeant" in a sentence
"It's interesting to see just how permeant virtual memory has become in our everyday lives."
""Brain permeant statins might be far more effective than statins that don't get into the brain," says Wolozin."
"It is certainly true that whatever is trapped inside needs to enhance vesicle replication as well as manufacture from permeant "nutrients" those factors that enhance membrane vesicle replication (since otherwise they would be diluted out as the vesicle replicates)."