The purchase of one futures contract and sale of another, in the expectation that the price relationships between the two will change so that a subsequent offsetting sale and purchase will yield a net profit. Examples include the purchase of one delivery month and the sale of another in the same commodity on the same exchange, or the purchase and sale of the same delivery month in the same commodity on different exchanges, or the purchase of one commodity and the sale of another (wheat vs. corn or corn vs. hogs), or the purchase of one commodity and the sale of products of that commodity (soybeans vs. soybean oil and soybean meal).