Relational Database: A database that follows E. F. Coddís 11 rules, a series of mathematical and logical steps for the organization and systemization of data into a software system that allows easy retrieval, updating, and expansion. An RDBMS stores data in a database consisting of one or more tables of rows and columns. The rows correspond to a record (tuple); the columns correspond to attributes (fields) in the record. In an RDBMS, a view, defined as a subset of the database that is the result of the evaluation of a query, is a table. RDBMSs use Structured Query Language (SQL) for data definition, data management, and data access and retrieval. Relational and object-relational databases are used extensively in bioinformatics to store sequence and other biological data.

Relational Database Management Systems (RDBMS): A software system that includes a database architecture, query language, and data loading and updating tools and other ancillary software that together allow the creation of a relational database application.

Restriction enzyme (restriction endonuclease): A type of enzyme that recognizes specific DNA sequences (usually palindromic sequences 4, 6, 8 or 16 base pairs in length) and produces cuts on both strands of DNA containing those sequences only. The "molecular scissors" of rDNA technology.

Reading frame: A sequence of codons beginning with an initiation codon and ending with a termination codon; also the way in which nucleotides are read in groups of three (codons) to specify the polypeptide coded by a gene.

Record: In a relational database, each record corresponds to a row (tuple) in a table.

Residue: A single unit in a polymer; used for both a single nucleotide in DNA or a single amino acid in a protein.