(n)stress, straindifficulty that causes worry or emotional tension“she endured the stresses and strains of life”, “he presided over the economy during the period of the greatest stress and danger” (R.J.Samuelson)
(n)strain, mental strain, nervous strain(psychology) nervousness resulting from mental stress“his responsibilities were a constant strain”, “the mental strain of staying alert hour after hour was too much for him”
(n)breed, strain, stocka special variety of domesticated animals within a species“he experimented on a particular breed of white rats”, “he created a new strain of sheep”
(n)form, variant, strain, var.(biology) a group of organisms within a species that differ in trivial ways from similar groups“a new strain of microorganisms”
(v)strain, extenduse to the utmost; exert vigorously or to full capacity“He really extended himself when he climbed Kilimanjaro”, “Don't strain your mind too much”