lowest terms
The fractions 2/4, 3/6, and 1/2 all describe the same amount — half of something. Among all these equal forms, 1/2 is the cleanest, because its top and bottom share no common factor bigger than 1. A fraction written this way is said to be in lowest terms, or simplest form.
To reduce a fraction to lowest terms, divide the numerator and the denominator by their greatest common factor. For 18/24, that common factor is 6, giving 3/4. You can also peel off shared factors one at a time: 18/24 = 9/12 = 3/4. The value never changes, only the appearance becomes simpler.
Lowest terms is the standard way to present a final answer, and it makes comparing fractions easier because two fractions are equal exactly when their lowest-terms forms match. A fraction is already in lowest terms when its numerator and denominator are relatively prime — sharing only the factor 1.
Reduce 24/36. The greatest common factor of 24 and 36 is 12, so 24/36 = (24÷12)/(36÷12) = 2/3.
Dividing top and bottom by their GCF gives the unique lowest-terms form.
Reducing only removes factors common to the whole numerator and the whole denominator. You cannot cancel a number that is merely a term, as in (3 + 4)/3 — the 3 on top is added, not multiplied, so nothing cancels.