Those letters spell natural.
The letters in "these letters" can spell the phrase "ether settles." The letters can spell shorter words such as trestles, sheerest, shelters, and treeless.
Those letters will spell strum.
Those letters will spell exciting.
Those letters will spell stigma.
Those letters spell arrest.
Those letters spell exchange.
Those letters spell vulnerable.
Those letters spell illness.
Those letters spell holiday.
Those letters spell opposite.
Those letters spell campaign.