| Feature | Definition |
|---|---|
| quality | Target column. A wine rating from an unknown source which ranges from 3 to 9 in the dataset. |
| alcohol | The ratio of ethonal to water in the wine. Unit is alcohol by volume or 'ABV'. |
| density | Measured in grams/milliliter. Used to help determine alcohol content. |
| pH | A measure of how acidic/basic the liquid is. The range is 0 to 14. 7 is neutral. Less than 7 is acidic and greater than 7 indicates a base. |
| fixed acidity | Acids left after a steam distillation test. Measured in g/L. |
| volatile acidity | Acids which can be removed by steam distillation. Measured in g/L. |
| citric acid | Most commonly used as an acid supplement during the fermentation process to help winemakers boost the acidity |
| residual sugar | Natural grape sugars left in a wine after the alcoholic fermentation finishes. Usually measured in grams per litre (g/L). |
| chlorides | The amount of salt in the wine. |
| total sulfur dioxide | The portion of SO2 that is free in the wine plus the portion that is bound to other chemicals. |
| free sulfur dioxide | SO2 that is present in wine but has not yet reacted with other chemicals. |
| sulphates | A combination of sulfur dioxide molecules and sulfite ions |
| type | Indicates if the wine is classified as a red or white. |