Dandruff and dry scalp are terms that are often used interchangeably, but these two conditions aren't one and the same. While dandruff flakes are dry, the condition itself is not caused by dry skin. Knowing the difference between dandruff flakes and a dry scalp can help you determine when to see a doctor for the right treatment.
Dandruff is technically defined as dead skin cells. This is a normal phenomenon that causes the characteristic white flakes to fall on your shoulders. Mild to moderate dandruff may be prevented with regular shampooing. These flakes are not caused by dry skin.
Dry scalp conditions are not the same as dandruff. Having dry skin can result in overall scalp dryness. This is remedied with moisturizing shampoos and conditioners. Yellow, oily flakes and silvery scales can accompany other types of dry skin conditions, which should be looked at by a doctor. Seborrheic dermatitis and psoriasis, for example, are not dandruff, though scalp flaking occurs with both these conditions.