to carry a torch for someone (also to hold a torch for someone)
informal phrase

- to be in love with someone, usually when they do not realize this

Macmillan Dictionary

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WORD ORIGIN

O! She doth teach the torches to burn bright
It seems she hangs upon the cheek of night
Like a rich jewel in an Ethiop's ear;
Beauty too rich for use, for earth too dear.

As this passage from Shakespeare's Romeo and Juliet shows, the torch has long been associated with passion and love. But even before Shakespeare, the ancient Greeks and Romans used the torch in marriage ceremonies. Brides customarily carried a torch to light the hearth in their new home. Hymen, the god of marriage ceremony, is often represented in paintings as a youth holding a torch, as is Venus, the goddess of love.

Apart from its reference to matters of the heart, the torch has taken on other meanings.

The Olympic torch, which was first used to light the Olympic flame at the 1936 Summer Olympics in Berlin, symbolises the transmission of Olympic ideals from ancient Greece to the modern world. And one of the most recognisable torches in the world can be found soaring above New York harbour, raised with one hand by the Statue of Liberty. It's meaning is open to interpretation, but the U.S. National Park Service, which maintains the 100-metre high copper statue, says:

"The torch is a symbol of enlightenment. The Statue of Liberty's torch lights the way to freedom, showing us the path to Liberty. Even the statue's official name represents her most important symbol: Liberty Enlightening the World.”

But exactly how the torch came to symbolise romantic obsession is not really clear. One theory concerns the eccentric Greek philosopher Diogenes (412-322 B.C.), who wandered around with a torch in a futile attempt to find an honest man.

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GOOD TO KNOW

If you travel to the United States and need a torch. In both British and American English, a torch can refer to a portable light produced by a flame from a stick or other flammable material. However, a battery-operated light is called a torch in the UK, but a flashlight in the US.

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SYNONYMS for being in love

to be smitten with, to be infatuated with, to be wild about, to be crazy about, to yearn for, to be hooked on, to be nuts about, to be stuck on, to be taken with, to fancy like mad

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SMUGGLE OWAD into a conversation, say something like:

"Mike has been CARRYING A TORCH for Simona ever since they were in college together.”