If the bridge has an adjustment then use that. If not it is more difficult and depends on the desin of the bridge- it may be possible to remove the saddle (strip that strings press on) and reduce its size - can be tricky. If you over reduce there is a danger of getting string buzz on some frets which may need CAREFULLY sanding down if they are too high.
raise the action (string elevation) lower the pickups springs or.. adjust the neck
Practice
A guitar has 6 strings. The vast majority of normal bass guitars only have 4, all of which produce lower tones.
Bass guitar by FAR. Even if you're talking about a bass flute, a bass guitar would still be almost 2 octaves lower.
The distance between the highest point of a fret and the strings. Different styles if playing may require different actions. Metal/shred will have lower ones while rock/blues will have higher ones. But a typical set up (measured from the top of the 17th fret to the bottom of each string) is around 4/64 if an inch.
The action on most acoustics can only be lowerd by sanding down the saddle. The saddle is the white bit the strings go over on the body of the guitar. Don't try this unless you know what you are doing because you could make your guitar extremely difficuly to play. If the action is too high it could also mean that the neck needs some adjusting. Once again, get someone who knows what they are doing. The best thing you could do to save yourself a lot of heart ache is to take your guitar to the local music shop and tell them what you want. This is not an expensive thing you are asking for.
Piano, because it can go higher and lower than a guitar.
The classical guitar is transposing because it is played an octave lower than read, I think.
An electric base guitar is usually tuned an octave lower than an electric lead guitar.
A bass guitar is an octave lower than a guitar, for example the first string on a guitar is an E string that produces an E note when struck, the first string on a four string bass guitar is an E also and when struck also produces an E note, just this note is an octave lower than the guitars
No, "lower" is not an action verb. It is a verb that indicates a change in position or level, but it is not considered an action verb in the traditional sense.
Lower.