These words pertain to the physical or mental application that is devoted to achieving a result. At its mildest, effort can be used in reference to measuring the amount of application a given task requires.

• How much effort will it take to get the orders out on time? It takes only a little effort to keep your shoes polished.

With a slight increase in force, it can stress a more than ordinary attentiveness or thoughtfulness: students who make an effort to note their own spelling errors; She decided to make a special effort to please him. When the word points specifically to a great outlay of energy, a challenging, difficult or unpleasant task is implied: a real effort to win the race; a crisis that will require all our will and effort to survive; What an effort it took to endure the blabbering old busybody without insulting her.

Exertion more readily suggests a considerable or exhausting outlay of effort : He stood gasping with exertion after reaching the summit of the hill; the mental exertion it took to make the accounts balance. Unqualified, the word is more likely to apply to physical effort , but not always: Students with low entry qualifications are expected to show greater exertion in their studies. Pains and trouble would also seem to stress outlay of effort in the face of difficulty or resistance, but both words are used idiomatically to indicate, instead, thoughtfulness or carefulness without necessarily suggesting great exertion .

• She took whatever pains necessary to put her guests at ease; He’d be a good worker if he’d only take the trouble to get to work on time.

Trouble in particular can be used ironically to suggest a small effort , whereas pains can as easily be used for exacting effort : taking great pains with every detail of the programme.

Struggle is the one word here that almost exclusively points to extreme efforts , those called up not only by the difficulty of the task or the external resistance to its achievement but by the determination, will or zeal of the actor as well: his heroic struggle to overcome all obstacles in a situation where it would have been an effort merely to stay alive. When qualified, however, the word need not always be so positive or approving: a feeble struggle to extricate himself; a hopeless struggle to escape his just punishment.