Complete the word analogy: ______ is to trail as grain is to grail (single letter change analogy).

Introduction / Context:
This analogy focuses on English word formation and the idea of creating new words by changing just one letter. The second pair grain and grail differ by a single letter. The task is to find a word that, when altered by one letter, produces trail in exactly the same way that grain changes to grail. Such questions assess your attention to spelling and letter patterns rather than vocabulary meaning alone.

Given Data / Assumptions:

• Analogy pattern: ______ : trail :: grain : grail.
• Known pair: grain and grail differ by one letter at the end, n changing to l.
• Options: path, holy, train, wheat.
• We assume that both sides of the analogy are built by a single letter change within a similar base word.

Concept / Approach:
The pair grain and grail share the letters g, r, a, i and differ only in the last letter, n versus l. Thus, the pattern is base word plus last letter change. To maintain parallel structure, we must find a base word that differs from trail in the same simple way, ideally by one letter substitution at one position. Among the choices, train is the closest candidate and can be turned into trail by changing the last letter n into l, mirroring the change from grain to grail.

Step-by-Step Solution:
Step 1: Examine the known pair. grain and grail both start with grai and differ only at the last letter: n becomes l. Step 2: Identify the pattern: change one letter at the end to form a new valid word. Step 3: Now look at the target word trail. We want a word from the options that can become trail by just changing one letter, preferably the final one. Step 4: Inspect train. The letters t, r, a, i are the same as in trail, and the difference is only at the last letter: train ends with n, trail ends with l. Step 5: Confirm that the transformation train → trail, by changing n to l, is structurally identical to grain → grail, where n changes to l as well.

Verification / Alternative check:
Check each remaining option: path cannot become trail by a single letter change. holy has a completely different pattern. wheat does not resemble trail in a single letter substitution manner. Only train differs from trail by exactly one letter, and specifically by n and l at the end. This perfect parallel to grain and grail confirms that train is the correct choice.

Why Other Options Are Wrong:
path: More than one letter would need to change to produce trail, so the word pair would not mirror grain and grail. holy: Has a different structure and does not convert to trail by a simple one letter substitution. wheat: Shares only some letters with grain and grail in a broad sense but does not map to trail in a parallel way.

Common Pitfalls:
A common mistake is to focus on meanings such as grain and wheat, which are semantically related, and choose wheat based on vocabulary similarity. However, this analogy is built on letter changes, not semantic categories. Always check whether the pattern is based on spelling, sound, or meaning before deciding which word continues the analogy.

Final Answer:
The word that behaves like grain does with grail is train, since train becomes trail with the same single letter change.