Ancient Elvish Art

There is therefore nothing intrinsic about the effects described in a given story that will tell you whether it is science fiction or fantasy. The classification of an effect as "fantastic" or "science fictional" is a matter of convention.

Hyperspace, time machines and scientists are conventions of science fiction; flying carpets, magical amulets and wizards are tropes of fantasy. This is an accident of the historical development of the genre.

In some cases they have overlapped: teleportation by matter-transmitter-beam is science fiction, teleportation by incantation is fantasy.

A hand-held cloaking device that confers invisibility is science fiction; a hand-held Ring of Power that confers invisibility is fantasy.

Mind-to-mind communication can be "psionics", or it can be an ancient elvish art. What matters is not the effect itself (generally scientifically impossible, though not always believed to be so by the authors) but the wider universe it is intended to evoke.

If it is one of space travel and proton-pistols, it gets classified as "science fiction", and the appropriate terms (cloaking device, matter-transmitter) are used; if it is one of castles, sailing ships and swords, it gets classified as "fantasy", and we instead speak of magic rings and travel by enchantment. In short, science fiction uses technology to explain impossible phenomena while fantasy employs magic.

Science fantasy - Non-human intelligent creatures