“Although” and “even though” are both subordinating conjunctions used to introduce a contrast or concession in a sentence. The primary difference between the two lies in their emphasis and the strength of contrast they convey.

“Although” is more commonly used in everyday language and is considered less emphatic compared to “even though.” It simply sets up a contrast without necessarily highlighting it intensively. For example: “Although it was raining, we went for a walk.” This sentence presents a contrast but does not emphasize the contradiction strongly.

On the other hand, “even though” carries a sense of emphasis and stronger contradiction. It signals that the contrast being highlighted is more salient or surprising. For example: “Even though he studied hard, he failed the exam.” In this sentence, the use of “even though” emphasizes the unexpected or contradictory nature of the situation.

In terms of altering the tone and meaning of a sentence, using “even though” tends to bring out a more forceful contrast or contradiction, while “although” may convey a more neutral or subtle contrast. The choice between these two conjunctions can influence the overall tone and mood of the sentence, affecting how the reader perceives the relationship between the contrasting elements.

In conclusion, while both “although” and “even though” serve the purpose of introducing contrast in a sentence, “even though” carries a stronger sense of emphasis and contradiction compared to “although,” impacting the tone and meaning of the sentence accordingly.