添加

1. Origins, structure, and basic meaning

• Structure: 添加 (てんか) means adding one substance to another. 添加した is the act; 添加物 is a compound noun for a substance added.
• Basic usage: A small amount of flavoring is added to dough, while a product description says no color-adjusting additive was used.

2. Common pitfalls and similar expressions

• Act of adding and substance being added
  • In 香料を添加した, flavoring is the added object; in 添加物, suffix 物 creates a material noun. The action and material are not the same part of speech.