General synonyms:
* Artificial: This is a very common synonym for synthetic, especially when referring to materials or substances.
* Man-made: This emphasizes the human origin of the substance.
* Manufactured: This highlights the process of creating the substance.
* Artificial: This implies a lack of natural origin.
* Fabricated: This is similar to "manufactured" but can also imply deception.
More specific synonyms:
* Synthetically produced: This emphasizes the process of production.
* Chemically synthesized: This refers to the specific method of production.
* Non-natural: This emphasizes the lack of a natural origin.
* Artificial: This is a general term for something created by humans.
Other options:
* Simulated: This is used for substances that mimic the properties of a natural substance.
* Imitation: This is used for substances that are intended to look or feel like a natural substance.
The best synonym will depend on the specific context and the nuance you want to convey.