Arising from the application of Optimality Theory (OT) to issues of language acquisition. the term "stratum" may represent (i) a single constraint. and therefore the strict ranking proposed by standard OT. as shown especially in research using data of the target language. https://www.roneverhart.com/Medline-Wheelchair-Arm-Trays-TRAY-ARM-WHEELCHAIR-ADJUSTABLE-LEFT-MDSR009636/