How to isolate duplicate strings in cell array?

I have a large cell array like:

words =

613×1 cell array

{'still'}

{'while'}

{'until'}

{'light'}

{'still'}

{'built'}

{'field'}

{'child'}

{'build'}

{'liked'}

{'until'}

{'plain'}

{'alike'}

{'alive'}

.

.

.

I am trying to isolate repeat words and output them in my command window

output:

'still'

'until'

How do I go about doing this? I am having issues with the unique function.

Thank you for your help!

Answer 1

[Mathieu NOE]

hello

here you are :

a = [    {'still'};
    {'while'};
    {'until'};
    {'light'};
    {'still'};
    {'built'};
    {'field'};
    {'child'};
    {'build'};
    {'liked'};
    {'until'};
    {'plain'};
    {'alike'};
    {'alive'}];

[C,IA,IC] = unique(a);
output = a;
output(IA) = [];