In technical and scientific writing, it is often necessary to repeat technical terms and to not use synonyms that might have slightly different meanings. It is important to choose exact terms and use them consistently.

Here is a simple explanation of why aerosol cans have curved bottoms. You’ll notice the author repeats key words, such as can, bottom, and product (highlighted in color), and does not vary the terms until the end, where he substitutes liquid for product. Such consistency of terms helps readers follow technical information.

The shape strengthens the structure of the can. If the can had a flat bottom, the force of the pressurized gas might push the metal outward. A curved bottom has greater structural integrity, just like an architectural arch or dome. With this shape, most of the force applied at the top of the curved metal is distributed to the sturdy edges of the can.

The shape makes it easier to use up all the product. Draining a flat-bottom can would be like sucking up the last little bit of a glass of water through a straw: You would have to tilt the can to one side so the product would collect under the plastic tube. With a curved bottom design, the last bit of product collects in the small area around the edges of the can. This makes it easier to empty almost all of the liquid.

—Tom Harris, “How Aerosol Cans Work”