These words are all used to describe someone or something that induces a state of dissatisfaction or weariness. Monotonous originally meant unvaried in inflection, cadence, pitch or tone: It was incredible that a lieder singer of her reputation should have such a monotonous voice. This meaning was later extended to refer to anything that is so lacking in variety as to cause fatigue or annoyance: The views from may train window grew monotonous after an hour or two and I found myself dozing off. Dull has many meanings, but in the sense being compared here, it is used to characterize a person or thing that is uninteresting because of a lack of variety, spirit, attraction, delight, etc.: a dull performer; a dull book; a dull meal. That which is boring may be dull or monotonous : a boring film unrelieved by dramatic conflict, wit or even a decent bit of acting. Boring , more than the other words in this group, can refer to that discontent and indifference known as ennui. This feeling may be a reaction to some person or thing, but it may also be the result of spiritual torpor and a general dissatisfaction with life. Tedious is like the preceding words in meaning but it goes beyond them in its suggestion that monotony or inactivity causes a repression of energy and an attendant physical discomfort: The month I spent confined to a hospital bed was so tedious that I couldn’t wait to get back to work. Tedious also refers to the kind of boredom one feels as a result of wordiness in speech or writing: The lecture was so tedious that people began to leave before it was half over. Tiresome , like tedious , implies fatigue: a tiresome day filled with exhausting household tasks. The word also has connotations of annoyance that are stronger than those in the four other terms: a very beautiful woman, but tiresome because of her bad temper.