What are bases? Definition:

As bases (English: base) refers to chemical compounds with a pH greater than seven. Bases act as so-called protonthat is, they are hydrogen ions (H+) from their reaction partners. The counterpart to bases are the acids. Both bases and alkalis are very corrosive depending on their concentration. Therefore, experiments must not be carried out without appropriate safety measures.
Often the distinction between lye and base, Both terms are often used interchangeably, whereas in principle nothing is wrong. Nevertheless, there is a small difference between alkali and base. The lye term is the older one and is usually found in old chemistry books. From today's understanding, a lye is an alkaline solution (meaning: liquid with a pH above 7), while the general term base is based more on the proton acceptor property (see above). The latter applies to all variants of basic substances. However, the liquor refers to an aqueous solution with alkaline / basic properties. So if you say that a lye is a base in aqueous solution, you're right. In summary: All bases are bases. But not all bases are alkalis.

Properties of bases:

Bases are corrosive.
Bases taste bitter (please do not try!).
Organic material is dissolved by bases.
Bases feel oily / soapy.
Most bases are water soluble.
Acids neutralize bases or alkalis.
The universal indicator turns purple.
Bases have a pH of about 7.5 - 14.
Bases are electrically conductive.

Examples of bases:

calcium hydroxide (Ca (OH)2): also known as slaked lime; Main component of mortar and responsible for its high pH
potassium hydroxide (KOH): base for potassium hydroxide
magnesium hydroxide (Mg (OH)2): naturally occurs as a mineral brucite
sodium (NaHCO3): also called soda; Part of baking soda, toothpaste and extinguishing agents
sodium hydroxide (NaOH): component of drain cleaners (caustic soda)