any substance such as manure or a mixture of nitrates used to make soil more fertile
"The farmer spread the fertilizer over the field to help the crops grow stronger."
A natural substance that is used to make the ground more suitable for growing plants.
"The farmer spread compost on the field as a natural fertilizer to enrich the soil before planting seeds."
In plain English: Fertilizer is stuff you put on plants to help them grow bigger and healthier by giving them extra food from the soil.
"The gardener mixed organic fertilizer into the soil to help his tomatoes grow better."
Usage: While often used interchangeably with manure, fertilizer specifically refers to any material added to soil to supply essential nutrients, which may include synthetic chemicals rather than just organic waste. In formal writing, prefer "fertilizer" over colloquial terms like "plant food."
Fertilizer comes from the verb fertilize with the suffix -er added to it. It originally referred to something or someone that makes things fertile.