These words denote anything that checks or halts progress, either in a literal or a figurative sense. Obstacle , barrier and hurdle present the most trouble in overcoming. An obstacle is something that one must either remove or go round before being able to proceed.

• The huge tree that had been blown down by the storm was an obstacle to traffic; Although the boy could speak fluently, his faulty enunciation was an obstacle to his being chosen for the school debating team.

A barrier is an obstacle or obstruction that temporarily impedes progress, but is not necessarily impassable.

• Writers never tire of depicting the barriers that arise between parents and growing children; The thick walls and moats of castles were surmount if he is to continue. Hurdle usually suggests challenge and a good probability of success: Every inventor faces many hurdles before his brain-child reaches the market as a finished product.

A bar may be either a physical obstacle or a condition that prevents entry or passage: the bars of the lion cage; race, colour or creed being no bar to membership. A barricade is always a physical obstacle , and is usually conceived of as being a hastily erected barrier against advancing soldiers, rioters or large crowds.

Impediment , in its literal meaning, suggests something that entangles the feet and interferes seriously with freedom of action or movement. There is a tendency to view an impediment as more or less permanent.

• His speech impediment made it nearly impossible for him to communicate with others; Legal insanity is an impediment to making contracts.

Snag is literally part of a dead tree which, lodged under the surface of a body of water, may damage boats or impede the flow of water. Figuratively, snag points to a hidden obstacle that one comes upon without warning and which is annoying or troublesome but rarely serious: Their plans for going into business sound ideal, but there is sure to be a snag somewhere.

Difficulty is the most general of the words in this group and may be applied loosely to any troublesome state of affairs: to have difficulty in learning higher mathematics; the difficulty of driving a car through deep mud; to have financial difficulties .