acid and base
"This theory not only defines acid and base but also clarifies their relation with each other. Acid and base are like the two sides of a coin. As either side of a coin cannot stay alone, acid and base also can't stay alone. Each of them has its counterpart which is named as conjugate."
METAMIA is a free database of analogy and metaphor. Anyone can contribute or search. The subject matter can be anything. Science is popular, but poetry is encouraged. The goal is to integrate our fluid muses with the stark literalism of a relational database. Metamia is like a girdle for your muses, a cognitive girdle.