A scale is "a series of notes differing in pitch according to a specific scheme," according to the Free Online Dictionary. In Western music, a scale spans an octave. An octave is composed of eight tones. There are major scales and minor scales. Major scales typically offer a sweeter sound, while minor scales sound a bit darker to the ear. If you are singing in a choir, it will help you to become familiar with all major and natural minor scales, as well as the key signatures for each.
The key signature consists of sharp and flat symbols. It appears at the beginning of every line of printed music. Most scales include at least one sharp or flat. Understanding the key signature will help you determine in what scale your music was written. For example, if you see a single F-sharp at the start of each line of your sheet music, you will know the piece was written in the key of G.
If you have been working in choirs for a while, you have probably been introduced to chords. When you sing triads in warm-ups, you are actually singing three separate pitches of a chord. In addition, during rehearsal, the soprano, alto, tenor and bass parts typically form a chord. All the same, it can be helpful to learn about some of the most commonly used chords--major, minor, diminished and augmented--to develop a comfort level with the chords and arpeggio formations standard to most Western choral music. If your choral group specializes in music of the 20th century and later, you may want to delve into understanding pentatonic and other scale types, as well as dissonant chords.
To develop top-notch sight-reading skills, you will need to develop a feeling for the various intervals. An interval, according to the Free Dictionary, is "the difference in pitch between two notes." A choral singer needs to internalize at least such intervals as thirds, fifths and octaves. A more advanced singer will be able to master half-step intervals, sixths, sevenths, even ninths. The more familiar you become with reproducing intervals, the more confident you will be when required to learn new music quickly.