Beau lines are horizontal grooves in the nail plate that occur when nail growth temporarily slows, which can occur after infection, trauma, or systemic illness.
[merckmanuals.com]
[…] when nail growth temporarily slows.
[pcds.org.uk]
(10-66%), onychogryphosis, onychomadesis, onychorrhexis, pitting, pressure changes, red spotted lunula, slowed growth, Terry’s nails, thickened plate, thinned plate, trachyonychia
[dermadvocate.net]