stratum (n.)

• band
• bed
• bedding
• belt
• blood
• bracket
• branch
• caste
• category
• clan
• class
• course
• deck
• division
• estate
• floor
• gallery
• grade
• group
• grouping
• head
• heading
• ionosphere
• kin
• label
• layer
• ledge
• level
• measures
• order
• overlayer
• photosphere
• pigeonhole
• plane
• position
• predicament
• race
• rank
• rating
• rubric
• seam
• section
• sept
• set
• shelf
• stage
• standing
• station
• status
• step
• story
• strain
• stratification
• stratosphere
• subdivision
• subgroup
• suborder
• substratum
• superstratum
• table
• thickness
• tier
• title
• topsoil
• tropopause
• troposphere
• vein
• zone