noun
1
BAD : The tiny light looked like a star in the horizon.
GOOD : The tiny light looked like a star on the horizon.
◆◆◆
on the horizon (NOT in ): 'The sun was setting on the horizon.'
2
BAD : Further education enables you to broaden your horizon.
GOOD : Further education enables you to broaden your horizons.
◆◆◆
your horizons (WITH - s ) = the range of things that you are involved or interested in: 'As a politician, his horizons extend no further than the next election.'