What is immunology? Immunology is the study of the immune system and is a very important branch of the medical and biological sciences. The immune system protects us from infection through various lines of defence. If the immune system is not functioning as it should, it can result in disease, such as autoimmunity, allergy and cancer.
What is an 'Invoice'. An invoice is a commercial document that itemizes a transaction between a buyer and a seller. If goods or services were purchased on credit, the invoice usually specifies the terms of the deal, and provide information on the available methods of payment. An invoice is also known as a bill or sales invoice. Next Up.
See also Voucher: an invoice is within the European union primarily legally defined by the EU VAT directive as an accounting voucher (to verify tax and VAT reporting) and secondly as a Civil law (common law) document.