The phrase "a weak relation" is correct and usable in written English.
It can be used to describe a connection or association that lacks strength or significance, often in academic or analytical contexts.
Example: "In this study, we found a weak relation between the two variables, suggesting that they do not significantly influence each other."
Alternatives: "a tenuous connection" or "a loose association".
The result shows the twist value of the TLs has a weak relation with the flare flux.
Our result showed that fluvial vegetation is not floristically differentiated according to its topographic position and there is a weak relation between pulse regime attributes and diversity of woody and herbaceous species.
In contrast, the relation in the social network of processing is a "weak relation".
Surprisingly, physical activity behaviour did not remain in the regression models, and only a weak relation to aerobic fitness was demonstrated (r = .163).163
Although it should be pointed out that the evidence about the Spanish Phillips curve mainly indicates a weak relation between inflation and unemployment see for example the survey by Gómez and Usabiaga (2001) and Caraballo and Usabiaga (2009b).
Atuahene-Gima (1996) confirms only the first phase of the channel, finding a significant contribution of market orientation on innovation, and a weak relation with market success, measured as performance by sales and profit.
The notion of reduction is a weaker relation than one-step reduction, and so it is useful to distinguish a subclass of terms using the stronger relation.
Moreover, studies examining more recent data samples tend to find a weaker relation between tangible assets and hedging, R&D and hedging, respectively.
Metrics relating to the timing of phenological events, such as start or mid of season showed a weaker relation and were not consistently relevant for carbon mapping.
This increased "noise" is evident in the WTA in Fig. 2, which shows a weaker relation to spiking activity at low threshold compared to high threshold.
