Not concentric
Not divided in parts.
Not accompanied by anything else; one in number.
Designed for the use of only one.
Performed by one person, or one on each side.
Not married, and (in modern times) not dating or without a significant other.
Having only one rank or row of petals.
Uncompounded; pure; unmixed.
To take the irregular gait called singlefoot.
To reduce (a railway) to single track.
To identify or select one member of a group from the others; generally used with out, either to single out or to single (something) out.
To thin out.
To get a hit that advances the batter exactly one base.
A score of one point, awarded when a kicked ball is dead within the non-kicking team's end zone or has exited that end zone.
A bill valued at $1.
A 45 RPM vinyl record with one song on side A and one on side B.
A tile that has a different value (i.e. number of pips) at each end.
A single cigarette.
A one-way ticket.
A handful of gleaned grain.
A popular song released and sold (on any format) nominally on its own though usually having at least one extra track.
A shot of only one character.
A score of one run.
A game with one player on each side, as in tennis.
One of the reeled filaments of silk, twisted without doubling to give them firmness.
A floating-point number having half the precision of a double-precision value.
One who is not married or does not have a romantic partner.
A hit in baseball where the batter advances to first base.