I am talking about valves, and there is this specific valve which is cheap (not expensive), compact (not too big), easy to maintain (the valve is easy to clean and rarely ever needs to be repaired) and easy to 'seal tight' (meaning, it is easy to tighly seal the valve).

The sentence which I wrote was 'These valves are cheap, compact, easy to maintain and seal tight.'

My teacher highlighted this sentence saying something was wrong with the sentence structure and that 'easy to seal tight' is incorrect. Is it true that it is incorrect? If yes, how should I rephrase it so that the sentence structure is correct?

  • to seal tightly
    – mplungjan
    Dec 3, 2013 at 14:58
  • 2
    "tight" modifies a verb, so according to grammar sticklers it should be an adverb: that is, "easy to seal tightly". English speakers have been using adjectives like this (called "flat adverbs") since Shakespeare. They are more common in the US than the UK, and (maybe because I'm American) I wouldn't say "easy to seal tight" is incorrect. Dec 3, 2013 at 14:59

1 Answer 1


I would argue that the main problem is that you've set up a parallel structure within a parallel structure, leaving either an invalid structure or an uncompleted parallelism. The default reading is "these valves are: a) cheap b) compact c) easy to maintain d) seal tight". Clearly, "These valves are seal tight" is not a valid construction. If we parse it the way you say you intended it, then there is no "and"-completion of the "these valves are" parallelism, so the sentence still fails to satisfy.

I'd recommend something like

These valves are cheap, compact, easy to maintain, and easy to seal tight [or tightly].


These valves are cheap, compact, and easy to maintain, and they seal tightly.

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