What does the negative half cycle of an AC waveform mean in single phase wiring?

An AC single phase electrical appliance has two wires Live and Neural. Neutral is always zero. If current changes its direction then it means that during negative half cycle the current should come from neutral and go back through the live wire to complete the circuit. But I doesn't happen. So what does negative waveform actually mean?

Yes it does happen. During one half of the AC cycle positive charge comes out of the positive terminal and during the other half cycle positive charge comes out of the negative terminal.

If positive charge comes out of the negative terminal then we must get shock by holding negative terminal, but it's not so..Please explain..

AC is between live and neutral. Zero can be assigned to live also. Assuming Neutral as zero is wrong

The easiest way to think of electricity is being like water going through pipes, driven by pressure.

In one cycle of AC, in the first half-cycle is like the water going one way through the pipe,
and then in the second half-cycle, the pressure changes to being in the opposite direction,
so then the water is driven back the other way.

The term "negative" means the pressure is in the opposite direction to the the first direction, so the water (or electrons) get driven the other way.

Household AC has the Neutral wire connected to ground.
The Live wire then alternates between being positive and negative pressure (electrical potential) with respect to the Neutral wire.

Does that help ?

Amardeep: from research
Ac waveform
Many signal waves, tend to be repetitive, or "periodic". They repeat a particular pattern or wave shape over a regular time period. The most important of all the different wave shapes is the sine wave, because any periodic wave can be shown to be made up of a series of pure sine waves, perhaps of many different frequencies and amplitudes. The sine wave is important to electronics engineers because of its purity, it consists of only a single frequency, it alternates regularly above and below its mid value at a constant rate. In a musical note this rate, the frequency, would be referred to as the pitch of the note. All waves except sine waves contain many different frequencies. They have one dominant frequency called "the fundamental", plus (often many) others called "harmonics", that give a wave its particular character.

Extra information:
Nikola Tesla, a Serbian-American scientist, electrical engineer, and inventor, developed the alternating-current (AC) electrical system, as well as radio, the Tesla coil transformer, wireless transmission, and fluorescent lighting.

Thanks for the analogous idea!!