The two words are actually synonyms, so "fabrication" could be making something new, and could also be used for making more of something or using a novel method for making something - you need to look at the context/the rest of the sentence.

One difference between "synthesis" and "fabricate".  You could fabricate something from ONE MATERIAL ONLY i.e. "the box was fabricated from steel", but you wouldn't say "the box was synthesised from steel".

(definitions from Google dictionary below)

fabrication - the action or process of manufacturing or inventing something.

synthesis

1.the combination of components or elements to form a connected whole.

"the synthesis of intellect and emotion in his work"

synonyms:

combination, union, amalgam, blend, mixture, compound, fusion, coalescence, composite, concoction, conglomerate, alloy; More 

2.the production of chemical compounds by reaction from simpler materials.

"the synthesis of methanol from carbon monoxide and hydrogen"

The two words are actually synonyms, so "fabrication" could be making something new, and could also be used for making more of something or using a novel method for making something - you need to look at the context/the rest of the sentence.

One difference between "synthesis" and "fabricate".  You could fabricate something from ONE MATERIAL ONLY i.e. "the box was fabricated from steel", but you wouldn't say "the box was synthesised from steel".

(definitions from Google dictionary below)

fabrication - the action or process of manufacturing or inventing something.

synthesis

1.the combination of components or elements to form a connected whole.

"the synthesis of intellect and emotion in his work"

synonyms:

combination, union, amalgam, blend, mixture, compound, fusion, coalescence, composite, concoction, conglomerate, alloy; More 

2.the production of chemical compounds by reaction from simpler materials.

"the synthesis of methanol from carbon monoxide and hydrogen"

Synthesis is a bottom-up approach however, fabrication is a top-down approach.

Synthesis - bottom-up methods to create/ modify discrete nanoscale structures or components;

Fabrication - top-down techniques and tools to create nanoscale to microscale features;

Manipulate/Assemble - methods to arrange/order/integrate discrete entities and make hierarchical structures.

I have a project to synthesize novel nanomaterials for the abstraction of pharmaceutical from aqueous system. Intend synthesizing metal nanopartcle and getting a nanofiber. What are the procedures to follow.

Although both terms are sometimes used alternatively, synthesis is a bottom-up approach using different methods (mostly chemicals and their reactions) to prepare nanomaterials from atomic and molecular levels. On the other hand, fabrication is a top-down approach which employs techniques and tools to make nanomaterials from bulk structures.

Visit also the following website:

https://cint.lanl.gov/capabilities/synthesis-fabrication.php