Polyesters can be defined as the condensation products of dicarboxylic acids with dihydroxy alcohols. This means that they are formed when these two types of compounds react together, resulting in the formation of a polyester molecule. Let's break down the answer in detail:

1. Definition of Polyesters:
- Polyesters are a class of polymers that contain ester functional groups in their main chain. They are commonly used in various applications such as textiles, packaging materials, and coatings due to their desirable properties like high strength, durability, and resistance to chemicals.

2. Condensation Reactions:
- Condensation reactions are chemical reactions in which two molecules combine to form a larger molecule, with the elimination of a small molecule such as water or alcohol. In the case of polyesters, the condensation reaction occurs between dicarboxylic acids and dihydroxy alcohols.

3. Dicarboxylic Acids:
- Dicarboxylic acids are organic compounds that contain two carboxylic acid functional groups (-COOH) in their structure. Examples of dicarboxylic acids commonly used in polyester synthesis include terephthalic acid, isophthalic acid, and adipic acid.

4. Dihydroxy Alcohols:
- Dihydroxy alcohols, as the name suggests, are organic compounds that contain two hydroxyl (-OH) groups in their structure. These compounds are also known as diols. Examples of dihydroxy alcohols used in polyester synthesis include ethylene glycol, propylene glycol, and 1,4-butanediol.

5. Condensation Reaction:
- When dicarboxylic acids and dihydroxy alcohols react together, a condensation reaction takes place. In this reaction, the carboxylic acid groups of the dicarboxylic acid react with the hydroxyl groups of the dihydroxy alcohol, resulting in the formation of an ester linkage (-COO-) and the elimination of a water molecule (H2O).

6. Polyester Formation:
- The condensation reaction between dicarboxylic acids and dihydroxy alcohols continues, forming a long chain of repeating ester units. This chain of ester units constitutes the polyester molecule.

In conclusion, polyesters are formed by the condensation reaction between dicarboxylic acids and dihydroxy alcohols. The carboxylic acid groups of the dicarboxylic acid react with the hydroxyl groups of the dihydroxy alcohol, resulting in the formation of ester linkages and the elimination of water molecules. This process continues, forming a long chain of repeating ester units, which make up the polyester molecule.

The polyestere contain dicorboxylic and diol mean dihydroxy